Electron beam system

ABSTRACT

Provided is an electron beam system, in which an electron beam emitted from an electron gun is irradiated to a stencil mask, and the electron beam that has passed through the stencil mask is magnified by an electron lens and then detected by a detector having a plurality of pixels so as to form an image of the sample.  
     Further, an etching apparatus for a sample such as a wafer and a stencil mask includes an inspection apparatus incorporated therein. The etching apparatus further comprises a load unit, a pattern forming unit, a cleaning unit, a drying unit and an unload unit. The etching apparatus receives the sample from a preceding step, applies respective processing to the sample by said respective units, and then transfers the processed sample to a subsequent step. A sample loading means, a sample unloading means and a transport means are not required for the transfer of the sample between respective units. Since the beam in a sheet-like configuration is irradiated to the stencil mask from its reverse side, and the transmission beam is image-projected and detected by a TDI detector, therefore a large number of pixels are imaged at the same time, thereby enabling an inspection with a high throughput.  
     Further, the present invention provides an electron beam system, in which a primary electron beam emitted from an electron gun is directed to a sample surface of a sample prepared as a subject to be inspected, and an electron image formed by a secondary electron beam emanated from the sample is magnified and detected, wherein an NA aperture is disposed on the path common to both of said primary electron beam and said secondary electron beam, an electron lens is disposed in the vicinity of said sample surface, and in this arrangement, a crossover produced by said electron gun, said electron lens and said NA aperture may be in the conjugate relationships to each other with respect to said primary electron beam.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an electron beam system that canprovide an evaluation, such as a defect inspection, for an electron beamtransmission mask with high throughput and high reliability, and furtherto a manufacturing method of a device to be used in such an electronbeam system.

[0002] In a common practice for a defect inspection of a variety ofmasks including a stencil mask according to an related art, a light suchas a visible ray is transmitted through the mask and an image therefromis detected by a CCD camera to thereby carry out the inspection(inspection by an optical system).

[0003] In a defect inspection apparatus of the above-described relatedoptical system, however, any defects having their size not greater than0.2 μm could not be detected.

[0004] Besides, although there has been one such device (an inspectionapparatus of SEM system) that allows an electron beam to scan a mask, inwhich secondary electrons emanated from this mask or back-scatteredelectrons therefrom are detected so as to inspect said mask for anypotential defects therein, yet said device has been suffered from aproblem of quite a long time required for the inspection.

SUMMERY OF THE INVENTION

[0005] The present invention has been made in the light of above-pointedproblems, and an object thereof is to provide an electron beam systemthat allows for an inspection for a minute defect with high throughputand high reliability, and also to provide a device manufacturing methodthat can improve a yield of device manufacturing by carrying out themask inspection using such a system.

[0006] According to an aspect of the present invention, there isprovided an electron beam system comprising an electron gun for emittingan electron beam and irradiating said electron beam against an sample,an electron lens for magnifying the electron beam that has passedthrough the sample, and a detector for detecting said magnified electronbeam and forming an image of the sample.

[0007] According to another aspect of the present invention, there isprovided a semiconductor manufacturing apparatus for a wafer or a mask,specifically a semiconductor manufacturing apparatus with an inspectionapparatus incorporated therein.

[0008] According to still another aspect of the present invention, thereis provided an electron beam system in which a primary electron beamemitted from an electron gun is irradiated onto a surface of a sample tobe inspected, and an electron image formed by a secondary electron beamemanated from the sample is magnified so as to be used for a detection,said system further comprising an NA aperture along an optical pathcommonly shared by said primary electron beam and said secondaryelectron beam, and an electron lens disposed in the vicinity of saidsurface of the sample, wherein a crossover created by said electron gunand said electron lens and said NA aperture are respectively in aconjugate relationship to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is an elevational view illustrating main components of aninspection apparatus according to an embodiment of a first invention,taken along the A-A line of FIG. 2A;

[0010]FIG. 2A is a plan view illustrating main components of theinspection apparatus shown in FIG. 1, taken along the B-B line of FIG.1;

[0011]FIG. 2B is a schematic sectional view illustrating anotherembodiment of a substrate carry-in unit in the first invention;

[0012]FIG. 3 is a sectional view illustrating a mini-environment unit ofFIG. 1, taken along the C-C line of FIG. 2A;

[0013]FIG. 4 is a sectional view illustrating a loader housing of FIG.1, taken along the D-D line of FIG. 2;

[0014]FIG. 5A is an enlarged side view of a mask rack;

[0015]FIG. 5B is a sectional view taken along the E-E line of FIG. 5A;

[0016]FIG. 6 shows a variation of a method for supporting a mainhousing;

[0017]FIG. 7 is a schematic view illustrating a general configuration ofan electron beam system (i.e., an electronic optical system) accordingto the present embodiment;

[0018]FIG. 8 is a schematic diagram of a defect inspection apparatusaccording to a variation of the first invention;

[0019]FIG. 9 shows a specific configuration of a detector of the defectinspection apparatus of FIG. 8;

[0020]FIG. 10 is a flow chart illustrating a flow of main routine of amask inspection in the defect inspection apparatus of FIG. 8;

[0021]FIG. 11 is a flow chart illustrating a detailed flow ofsub-routine in a step for acquiring a plurality of image data to beinspected (Step 1304) of FIG. 10;

[0022]FIG. 12 is a flow chart illustrating a detailed flow ofsub-routine in a comparing step (Step 1308) of FIG. 10;

[0023]FIG. 13 shows an example of a plurality of images to be inspected,which has been obtained by the defect inspection apparatus of FIG. 8,and a reference image;

[0024]FIG. 14 is a conceptual diagram showing a plurality of regions tobe inspected, which are partially overlapped one on the other whilebeing offset from each other over the surface of the mask;

[0025]FIG. 15A is a schematic diagram illustrating an electron beamsystem according to another embodiment of the first invention;

[0026]FIG. 15B is a schematic plan view illustrating an aspect ofscanning of a sample by using a plurality of primary electron beamsgenerated by the embodiment shown in FIG. 15A;

[0027]FIG. 16 is a flow chart illustrating an embodiment of amanufacturing method of a semiconductor device according to the firstinvention;

[0028]FIG. 17A is a flow chart illustrating a lithography processrepresenting a core step in a wafer processing process shown in FIG. 16;

[0029]FIG. 17B is a flow chart illustrating a procedure of a defectinspection of a mask;

[0030]FIG. 18 is a schematic diagram illustrating a principle of asecond invention;

[0031]FIG. 19 a block diagram illustrating an exemplary flow of steps ofthe second invention;

[0032]FIG. 20 is a schematic diagram illustrating a related systeminvolved in the second invention;

[0033]FIG. 21 is a block diagram illustrating an exemplary flow of stepsof the related system involved in the second invention;

[0034]FIG. 22 is a schematic diagram illustrating a second embodiment ofthe second invention;

[0035]FIG. 23 is a schematic diagram illustrating a differentialexhausting section;

[0036]FIG. 24 is a schematic diagram illustrating a third embodiment ofthe second invention;

[0037]FIG. 25 is a schematic diagram illustrating a fourth embodiment ofthe second invention;

[0038]FIG. 26 is a schematic diagram illustrating an electron beamirradiation method of FIG. 25;

[0039]FIG. 27 is a schematic diagram illustrating an optical system ofan electron microscope of image projection type using back-scatteredelectrons;

[0040]FIG. 28 is a flow chart illustrating an embodiment of a method ofprocessing by using a system according to an embodiment of the secondinvention;

[0041]FIG. 29 is a general view of an electron beam system according toa first embodiment of a third invention;

[0042]FIG. 30 is a detail view illustrating a part of the electron beamsystem according to the first embodiment of the third invention;

[0043]FIG. 31 is an explanatory diagram for a cosine law;

[0044]FIG. 32(a) is a plan view of a shaping aperture;

[0045]FIG. 32(b) is an intensity distribution map of an image of aprimary electron beam irradiated onto a sample through the shapingaperture;

[0046]FIG. 33 is an intensity distribution diagram of the primaryelectron beam in respective sectional planes of FIG. 32(b);

[0047]FIG. 34 is a detail view illustrating a part of an electron beamsystem of a second embodiment of the third invention;

[0048]FIG. 35 is an explanatory diagram illustrating a variation ofdistortion as a function of different distance L between a position onwhich a magnified image is formed and a magnifying lens;

[0049]FIG. 36 is an explanatory diagram for a third and a fifth order ofdistortion; and

[0050]FIG. 37 is a schematic sectional view or an end view of anobjective lens (an electromagnetic lens).

DETAILED DESCRIPTION OF THE INVENTION

[0051] First of all, an outline of an electron beam system according toan embodiment of a first invention will be described.

[0052] [1] This electron beam system is defined as such an electron beamsystem, in which an electron beam emitted from an electron gun isirradiated to a sample, and the electron beam that has passed throughthe sample is magnified by an electron lens and further detected by adetector having a plurality of pixels so as to form an image of thesample.

[0053] [2] In the electron beam system, the sample may be a stencilmask.

[0054] [3] In the electron beam system, the electron beam to beirradiated may be an electron beam of good collimation.

[0055] [4] In the electron beam system, the optical system forirradiation may comprise at least one shaping aperture, wherein an imageof the shaping aperture may be formed onto a surface of the sample.

[0056] [5] In the electron beam system, the shaping aperture maycomprise a plurality of shaping apertures disposed in the vicinity of anoptical axis, and in another system, an area of the sample subject tothe irradiation may be modified by changing an overlap between theshaping apertures to each other.

[0057] [6] In the electron beam system, the electron gun may comprise athermal electron emission cathode, so that the electron gun can beoperated under a space-charge-limited-condition.

[0058] [7] In the electron beam system, the electron beam system mayfurther comprise at least a two-stage of electron lenses and at leastone shaping aperture, wherein a primary ray exiting from the shapingaperture may be irradiated in a collimated state onto the sample.

[0059] [8] In the electron beam system, the optical system forirradiation may comprise an entrance pupil of an irradiation lenssystem, wherein a source image may be formed on the entrance pupil.

[0060] [9] In the electron beam system, a magnification of a magnifyinglens may be made variable in dependence on a size of an irradiation areaof the electron beam.

[0061] [10] In the electron beam system, the irradiation area of theelectron beam may be specified as a rectangular shape having long sidesand short sides, wherein a detection (evaluation) of the sample may becarried out while continuously moving a sample table carrying the samplein the direction along the short sides.

[0062] [11] In the electron beam system, the electron beam may be drivento scan in a step-by-step manner or in a sequential manner.

[0063] [12] In the electron beam system, the detector may comprise ascintillator, a CCD detector and an optical lens, wherein a size of animage formed by the scintillator may be adjusted by using the opticallens so that the image may be formed on a CCD plane in the CCD detector.

[0064] [13] In the electron beam system, the electron gun may bedesigned as such an electron gun of small electron source image havingan FE, a TFE, or a Schottky cathode.

[0065] [14] In the electron beam system, the electron gun may bedisposed under the sample and the detector for detecting a defect in thesample may be disposed above the sample or a stencil mask.

[0066] [15] In the electron beam system, a plurality of magnifyinglenses for magnifying the electron beam may be disposed between theelectron gun and the detector, and further the magnifying lens servingfor magnifying the electron beam that has passed through the sample (avariety of masks) firstly among the others may be a doublet lens.

[0067] [16] In the electron beam system, the magnifying lens maycomprise an NA aperture, wherein the magnifying lens may be designedsuch that any electron beams having bad property in collimation, whichhave been scattered on the sample, can be eliminated by the NA aperture.In a specific configuration thereof, the NA aperture is disposed betweencomponents of the doublet lens.

[0068] [17] In the electron beam system, the detector may be configuredsuch that an MCP and a scintillator may be placed in a vacuumenvironment, which is followed by a relay optical system serving also asa vacuum window and a CCD detector or a TDI detector in this sequence.

[0069] [18] In the electron beam system, the relay optical system andthe CCD detector, or the relay optical system and the TDI detector maybe disposed in a vacuum environment.

[0070] [19] In the electron beam system, the image detector may comprisean MCP, an EB-CCD detector or an EB-TDI detector.

[0071] [20] In the electron beam system, a detector serving fordetecting secondary electrons or back scattered electrons may be placedin an electron gun side of the sample, and by changing a focal length ofthe lens, a crossover image of small size may be formed on a surface ofthe sample so as to scan it, thereby carrying out the registration ofthe sample.

[0072] [21] In the electron beam system, a detector serving fordetecting secondary electrons or back scattered electrons may be placedin an electron gun side of the sample, and further an electron beam ofsmall size may be formed by reducing an overlap between two shapingapertures, which is used to form a crossover image on a surface of thesample and to scan it, thereby carrying out the registration of thesample.

[0073] [22] In the electron beam system, an equivalent scan frequencyper pixel may be set to be higher than 200 MHz.

[0074] [23] In the electron beam system, a defect inspection of a samplemay be carried out by comparing an image data obtained by an electronbeam that has passed through the sample with a previously stored patterndata.

[0075] [24] In the electron beam system, a defect in a stencil mask maybe detected by irradiating an electron beam emitted from an electrongun, against a stencil mask and then by detecting the electrons thathave passed through the stencil mask.

[0076] [25] In the electron beam system, the electron beam system maycomprise a plurality of optical systems, wherein the term “a pluralityof optical systems” refers to such a form that comprises a plurality ofoptical systems for irradiation including electron guns and a pluralityof detectors including detecting sensors, each of the optical systemsfor irradiation corresponding to each of the detectors in one-by-onemanner.

[0077] [26] The electron beam system may be used to provide amanufacturing method of a semiconductor device using a stencil mask thathas experienced a defect inspection.

[0078] One specific example may be a manufacturing method of asemiconductor device comprising the following steps:

[0079] (a) a step for manufacturing a mask;

[0080] (b) a step for inspecting the manufactured mask by using theelectron beam system; and

[0081] (c) a step for manufacturing a variety of chips by using the maskthat has experienced a defect inspection.

[0082] Further, the electron beam system may be applied also to alithography step in the wafer processing process. In that case, in orderto selectively process a layer of thin film, a wafer substrate and thelike, a mask that has been inspected by the electron beam system may beused to form a resist pattern.

[0083] A preferred embodiment of a first invention will now be describedwith reference to the attached drawings, taking by way of example asemiconductor inspection apparatus serving for inspecting a substrate ora mask (e.g., a stencil mask) having a patterned surface as an object ofthe inspection.

[0084]FIGS. 1 and 2A show main components of a semiconductor inspectionapparatus 1 of the present embodiment in an elevational view and a planview.

[0085] The semiconductor inspection apparatus 1 of this embodimentcomprises: a cassette holder 10 for holding a cassette containing aplurality of masks “M”; a mini-environment unit 20; a main housing 30defining a working chamber; a loader housing 40 located between themini-environment unit 20 and the main housing 30 and defining twoloading chambers; a loader 60 for picking up the masks from the cassetteholder 10 and loading it on a sample table 50 located within the mainhousing 30; and an electron beam system 70 disposed in the main housing30, all of which are arranged in such a physical relationship asdepicted in FIGS. 1 and 2A.

[0086] Cassette Holder

[0087] The cassette holder 10 is designed to hold a plurality (twopieces in this embodiment) of cassettes “c” (e.g., a closed cassette,such as SMIF, FOUP, manufactured by Assist Inc.), each containing aplurality (e.g., five pieces) of masks M placed side by side in parallelwith each other along the up and down direction. This cassette holdermay employ a suitable structure depending on the specific casesselectively such that for the case where the cassette is transferred bya robot or the like and loaded onto the cassette holder 10automatically, a specific suitable structure therefor may be employedand that for the case where the loading operation is manually carriedout, an open cassette structure suitable therefor may be employed. Inthis embodiment, the cassette holder 10 has employed a system forautomatically loading the cassette c, and comprises, for example, anelevating table 11 and an elevating mechanism 12 for moving up and downthe elevating table 11, wherein the cassette c can be set on theelevating table 11 automatically in a state illustrated by the chainline in FIG. 2A, and after having been set, the cassette c is rotatedautomatically into an orientation illustrated by the solid line in FIG.2A for heading to an axial line of rotational movement of a firsttransport unit within the mini-environment unit. Further, the elevatingtable 11 is lowered into the position indicated by the chain line inFIG. 1. Thus, the cassette holder used in the case of the automaticloading or the cassette holder used in the case of the manual loadingmay appropriately employ any known structures, and detailed descriptionof its structure and function should be herein omitted.

[0088] In an alternative embodiment, as shown in FIG. 2B, a plurality ofmask substrates is accommodated in a state where they are contained inslot-type pockets (not shown) secured firmly to the inner side of a boxmain body 501, so that those mask substrates may be transferred andstored in this state. This substrate carrier box 24 consists of arectangular parallelepiped box main body 501; a substrate carry-in andcarry-out door 502, which joined with an automatic opening and closingsystem therefor so that an opening formed in a side surface of the boxmain body 501 may be opened and closed automatically; a lid 503 forcovering another opening located opposite to the door opening servingfor attaching/detaching filter elements and a fun motor; slot-typepockets (not shown) for holding substrates W; a ULPA filter 505; achemical filter 506; and a fan motor 507. In this embodiment, thesubstrates are taken in and out by a first transport unit 612 of a robotsystem.

[0089] It is to be noted that the substrates or the masks M contained inthe cassette c are those subject to the inspection, and such aninspection may be carried out after or in the course of a process forprocessing the mask in the series of processes for manufacturing thesemiconductor. Specifically, those substrates or the masks that haveexperienced the film-depositing step, the etching step, the ionimplantation step and the likes, or those masks that have been patternedon the surfaces thereof may be accommodated in the cassette. Since anumber of those masks are accommodated in the cassette c so as to bespaced in parallel from each other along the up and down direction, anarm of the first transport unit is adapted to move up and down so thatthe mask in a desired position can be held by the first transport unit,as will be described later.

[0090] Mini-environment Unit

[0091] In FIGS. 1 through 3, the mini-environment unit 20 comprises: ahousing 22 defining a mini-environment space 21 of which atmosphere maybe controlled; a gas circulator 23 for providing the atmosphere controlby circulating a gas such as a clean air within the mini-environmentspace 21; an exhausting device 24 for recovering and then exhausting aportion of the air supplied into the mini-environment space 21; and apre-aligner 25 arranged within the mini-environment space for providinga coarse alignment of a substrate or a mask subject to an inspection.

[0092] The housing 22 comprises a top wall 221, a bottom wall 222 andcircumferential walls 223 surrounding four circumferential portions soas to provide a structure to separate the mini-environment space 21 froman external environment. In order to provide the atmosphere control ofthe mini-environment space, the gas circulator 23 comprises, as shown inFIG. 3, a gas supply unit 231 which is attached to the top wall 221within the mini-environment space 21 for cleaning the gas (the air inthis illustrate embodiment) and then directing a laminar flow of thuscleaned air right below through one or more gas blowoff openings (notshown); a recovery duct 232 located on the bottom wall 222 within themini-environment space for recovering the air that has flown down towardthe bottom; and a conduit 233 interconnecting the recovery duct 232 andthe gas supply unit 231 for returning the recovered air back to the gassupply unit 231. In this embodiment, the gas supply unit 231 is designedto intake about 20% of the supply air from the outside of the housing 22for cleaning, but the ratio of the gas to be taken in from the outerenvironment may be arbitrarily selected. The gas supply unit 231comprises a HEPA or ULPA filter of a known structure to create a cleanair. The laminar flow of the clean air directed downward, or the downflow, is supplied such that it can flow mainly through a conveyingsurface of the first transport unit located within the mini-environmentspace 21, as will be described later, to thereby prevent any dust whichmay possibly produced by the transport unit from adhering to the mask.Consequently, the blowoff opening for the down flow may not necessarilybe arranged in a location near the top wall as illustrated but it may bearranged in a level above the conveying surface defined by the transportunit. Also, the down flow may not necessarily flow entirely across themini-environment space. It is to be noted that depending on eachparticular case, the cleanliness may be ensured by using an ionic air asthe clean air. Further, a sensor for observing the cleanliness in themini-environment space may be provided therein, so that an operation ofthe unit may be shut down when the cleanliness is degraded. An accessport 225 is formed in a location of the circumferential wall 223 of thehousing 22 adjacent to the cassette holder 10. A shutter system of aknown structure may be arranged in the vicinity of the access port 225so that the access port 225 can be closed from the mini-environment unitside. The laminar down flow created in the vicinity of the mask may beat a flow velocity of 0.3-0.4 m/sec, for example. The gas supply unitmay not necessarily be disposed within the mini-environment space butmay be disposed external to the mini-environment space.

[0093] The exhausting device 24 comprises: a suction duct 241 disposedin a location lower than the mask conveying surface of the transportunit and in the lower portion of the transport unit; a blower 242disposed external to the housing 22; and a conduit 243 forinterconnecting the suction duct 242 and the blower 242. This exhaustingdevice 24 sucks the gas flowing down along the circumference of thetransport unit and containing the dust which may be possibly produced bythe transport unit, through the suction duct 241, and exhausts that airto the outside of the housing 22 via the conduits 243, 244 and theblower 242. In that case, the air may be exhausted through an exhaustpipe (not shown) laid near the housing 22.

[0094] The pre-aligner 25 disposed within the mini-environment space 21is designed to detect optically or mechanically a contour of the maskand to provide in advance an alignment of the mask in the rotationaldirection around the axis line O-O of the mask within an accuracy of +1degree. The pre-aligner is a constitutional part of a mechanism fordetermining a coordinate of a subject to be inspected in accordance withclaims of the present invention, and takes a role for providing a coarsealignment of the subject to be inspected. Since the pre-aligner may beof any known structure, therefore the description on its structure andfunction should be omitted.

[0095] It is understood that although it is not shown, a recovery ductfor the exhausting device may also be provided under the pre-aligner sothat the air containing dust from the pre-aligner can be exhausted tothe outside.

[0096] Main Housing

[0097] In FIG. 1 and FIG. 2, the main housing 30 defining the workingchamber 31 comprises a housing main body 32, which is supported by ahousing supporting device 33 loaded on a vibration insulating device ora vibration isolating device 37 located on a table frame 36. The housingsupporting device 33 comprises a frame structure 331 assembled into arectangular shape. The housing main body 32 is disposed and mountedsecurely onto the frame structure 331 and comprises a bottom wall 321loaded on the frame structure, a top wall 322 and circumferential walls323 connected to both of the bottom wall 321 and the top wall 322 tosurround four circumferential portions, thereby isolating the workingchamber 31 from the outside. Although the bottom wall 321 is shown, inthis embodiment, to be made of relatively thick steel plate in order toprevent any displacement from being induced from the loading of thedevices, such as a sample table, loaded thereon, other structures may beemployed. In this embodiment, the housing main body and the housingsupporting device 33 have been assembled in a rigid structure, whereinthe vibration isolating device 37 prevents the vibration from the flooron which the table frame 36 is installed from being transmitted to thisrigid structure. An access port 325 for taking in and out the mask isformed in one circumferential wall among those circumferential walls323, which is adjacent to a loader housing, which will be describedlater.

[0098] It is to be understood that the vibration isolating device may beof active type having an air spring, a magnetic bearing and the like, oralternatively of passive type having the same elements. Either of thetypes may have a known structure, and the description on its structureand function should be herein omitted. The working chamber 31 isdesigned to be held in a vacuum atmosphere by a vacuum device (notshown) having a known structure. A controller 2 for controlling anoverall operation of the apparatus is located under the table frame 36.

[0099] Loader Housing

[0100] Referring to FIGS. 1, 2 and 4, the loader housing 40 comprises ahousing main body 43 defining a first loading chamber 41 and a secondloading chamber 42. The housing main body 43 comprises a bottom wall431, a top wall 432, circumferential walls 433 surrounding fourcircumferential portions and a partition wall 434 for separating thefirst loading chamber 41 and the second loading chamber 42, so that bothloading chambers may be isolated from the external environment. Anaccess port 435 is formed in the partition wall 434 for passing the maskM between two loading chambers. Further, access ports 436 and 437 areformed in locations of the circumferential walls 433 adjacent to themini-environment unit and the main housing, respectively. The housingmain body 43 of this loader housing 40 is mounted on and supported bythe frame structure 331 of the housing supporting device 33.Accordingly, this loader housing 40 is also designed to be protectedfrom any vibrations otherwise transmitted from the floor. The accessport 436 of the loader housing 40 and the access port 226 of the housing22 of the mini-environment unit are aligned and interconnected with eachother, and in a connecting point therebetween a shutter system 27 isarranged so as to selectively block the communication between themini-environment space 21 and the first loading chamber 41. The shuttersystem 27 includes a sealing member 271 surrounding the circumferencesof the access ports 226 and 436 and fixedly secured in tight contact tothe side wall 433, a door 272 working cooperatively with the sealingmember 271 so as to block an air passage through the access ports, and adriving device 273 for driving that door. Further, the access port 437of the loader housing 40 and the access port 325 of the housing mainbody 32 are aligned and interconnected with each other, and in aconnecting point therebetween a shutter system 45 is arranged so as toselectively seal and block the communication between the second loadingchamber 42 and the working chamber 31. The shutter system 45 includes asealing member 451 surrounding the access ports 437 and 325 and fixedlysecured in tight contacts to the side walls 433 and 323, a door 452working cooperatively with the sealing member 451 so as to block an airpassage through the access ports, and a driving device 453 for drivingthat door. Further, the opening formed in the partition wall 434 isprovided with a shutter system 46 which selectively seals and blocks thecommunication between the first and the second loading chambers byclosing a door 461. Those shutter systems 27, 45 and 46 are designed toprovide an airtight sealing to each chamber when they are in the closedpositions. Those shutter systems may be of any known systems, and thedetailed description on its structure and function should be hereinomitted. It is to be noted that since the method for supporting thehousing 22 of the mini-environment unit 20 is different from that forsupporting the loader housing, in order to prevent the vibration fromthe floor from being transmitted to the loader housing 40 and the mainhousing 30 via the mini-environment unit 20, a cushion member forvibration isolation should be arranged between the housing 22 and theloader housing 40 such that it may surround the circumferences of theaccess ports to be air-tight.

[0101] In the first loading chamber 41, a mask rack 47 is arranged,which holds a plurality (two pieces in this embodiment) of masks M in ahorizontal state to be spaced from each other in the up and downdirection. The mask rack 47, as shown in FIG. 5, comprises four supportstruts 472 fixed in an upright state to a rectangular base board 471 inits four corners as spaced from each other, each one of the supportstruts defining double steps of supporting sections 473 and 474, whereinthe mask M is supported by the support struts 472 with its peripheraledge carried on the supporting sections. Thus constructed mask rack 47allows a first or a second transport unit, which will be describedlater, to extend a tip of an arm thereof through a space betweenadjacent supporting struts so as to approach and grip the mask by itsarm.

[0102] The loading chambers 41 and 42 are adapted to have the atmospherecontrolled to be high vacuum condition (in a range of 10⁻⁵ to 10⁻⁶ Pa asa vacuum level) by the aid of a well-known vacuum exhausting device (notshown) including vacuum pump, though not shown. In that case, the firstloading chamber 41 may be held in a lower vacuum atmosphere as a lowvacuum chamber, while the second loading chamber 42 may be held in ahigher vacuum atmosphere as a high vacuum chamber, thereby providing aneffective way to prevent the contamination of the mask. Employing such aconfiguration can help transfer the subsequent mask that is accommodatedin the loading chamber and going to be subjected to a defect inspectioninto the working chamber without delay. Employing such loading chambersmay help improve the throughput of the defect inspection byassociatively working with an electron beam system, which will bedescribed later, and further help maintain the vacuum level in thesurrounding of the electron beam source, which is required to be held ina high vacuum condition, at as high vacuum condition as possible.

[0103] The first and the second loading chambers 41 and 42 are connectedwith a vacuum exhausting pipe and a vent pipe for an inactive gas (e.g.,purified dry nitrogen), respectively (either not shown). With thisarrangement, the atmospheric condition in each loading chamber can beachieved by the inactive gas vent (the inactive gas is injected toprevent an oxygen gas and the like other than the inactive gas fromadhering to the surface). The device that can provide such an inactivegas vent may have a well-known configuration, and the detaileddescription thereof should be omitted.

[0104] It is to be noted that in an inspection apparatus using anelectron beam according to the present invention, it is important that asubstance represented by lanthanum hexaboride (LaB₆) that can be used asan electron beam source of an electronic optical system, which will bedescribed later, should not be brought into contact with oxygen or thelike as much as possible after once having been heated up to such a hightemperature where the thermal electron has been emitted therefrom inorder not to reduce a lifetime thereof, and this can be ensured byapplying the atmosphere control as described above to the workingchamber in which the electronic optical system is installed, in a stepprior to a transfer operation of the mask thereinto.

[0105] Sample Table

[0106] The stage device or the sample table 50 comprises: a stationarytable 51 located on the bottom wall 321 of the main housing 30; a Ytable 52 operatively mounted on the stationary table to be capable ofmoving in the Y direction (the direction orthogonal to the sheet surfacein FIG. 1); an X table 53 operatively mounted on the Y table to becapable of moving in the X direction (the left and right direction inFIG. 1); a turntable 54 capable of rotating on the X table; and a holder55 located on the turntable 54. A mask M is releasably loaded on a maskloading surface 551 of the holder 55. The holder may have a knownstructure allowing for the mask to be releasably gripped in a mechanicalmanner or by an electrostatic chuck system. The sample table 50 isadapted to provide a highly precise alignment of the mask held in theholder on the loading surface 551 with respect to the electron beamirradiated from the electronic optical system in the X direction, Ydirection and Z direction (i.e., the up and down direction in FIG. 1) aswell as the rotational direction around the axial line orthogonal to thesupporting surface of the mask (i.e., the θ direction), by actuating theplurality of tables described above using a servo motor, an encoder anda variety of sensors (not shown). It is to be noted the positioning inthe Z direction may be achieved by, for example, making the position ofthe loading surface on the holder to be fine-tunable. In theseoperations, a reference position of the loading surface is detected by aposition measuring device employing laser of very fine diameter (laserinterference range finder using a principle of interferometer) and theposition is controlled by a feedback circuit, though not shown, and inassociation with or instead of the above control, the position of thecontour of the mask is measured to detect a position within a plane anda rotational position of the mask with respect to the electron beam, andthe turntable is rotated by, for example, a stepping motor capable offine angle controlling so as to control the position of the mask. Inorder to prevent or minimize, if any, a production of dust within theworking chamber, the servo motors 521 and 531 and the encoders 522 and532 for the sample table are disposed external to the main housing 30.It is to be noted that the sample table 50 may be of known structureused in, for example, a stepper, and the detailed description on itsstructure and operation should be herein omitted. Also, the laserinterference range finder may be of known structure, and the detaileddescription on its structure and operation should be omitted.

[0107] The reference can be set for the signal obtained by inputting inadvance the rotational position and/or the position in the X- andY-directions of the mask with respect to the electron beam to a signaldetecting system or an image processing system, both of which will bedescribed later. Further, the mask chuck mechanism disposed in thisholder is configured such that a voltage required to chuck the mask maybe applied to an electrode of the electrostatic chuck, in which the maskis pushed at three points in its periphery (preferably, equally spacedalong the circumference) for its positioning. The mask chuck mechanismcomprises two stationary positioning pins and one press-type crank pin.The crank pin is designed to achieve an automatic chuck and automaticrelease, and also to define a conducting point of the voltageapplication.

[0108] It is to be noted that in this illustrated embodiment, the tablemoving in the left and right direction in FIG. 2 has been designated asthe X table and the table moving in the up and down direction gas beendesignated as the Y table in FIG. 2, and without any trouble, the tablemoving in the left and right direction may be designated as a Y tableand the table moving in the up and down direction may be designated asan X table.

[0109] Loader

[0110] The loader 60 comprises a first transport unit 61 of a robotsystem located within the housing 22 of the mini-environment unit 20 anda second transport unit 63 of a robot system located within the secondloading chamber 42.

[0111] The first transport unit 61 has a multi-joint arm 612 capable ofrotating around an axial line O₁-O₁ with respect to a driving section611. The multi-joint arm may employ any arbitrary structure, and in thisembodiment, it includes three parts operatively joined so as to bemovable rotationally with respect to each other. A first part of the arm612 of the first transport unit 61, which is one of the three partslocated in the closest position to the driving section 611, is attachedto a shaft 613 which may be driven to rotate by a driving mechanism ofknown structure (not shown) arranged in the driving section 611. The arm612 can rotate around the axial line O₁-O₁ with the aid of the shaft613, while it can be extended or contracted in the radial direction withrespect to the axial line O₁-O₁ as a whole unit by a relative rotationamong the parts. A tip portion of a third part of the arm 612, which isone of those parts located in the farthest position from the shaft 613,is provide with a gripping device 616 for gripping the mask, which isimplemented by a mechanical, electrostatic or other type chuck of knownstructure. The driving section 611 is allowed to move in up and downdirection by an elevating mechanism 615 of known structure.

[0112] In this first transport unit 61, the arm 612 is extended towardeither one of the directions for M1 and for M2 between two cassettes cheld in the cassette holder, and one piece of mask accommodated in thecassette c is placed onto the arm or gripped by the chuck (not shown)attached to the tip portion of the arm, so as to be taken out of it.After that, the arm is contracted (into the state shown in FIG. 2), andthen is rotated and stopped at a position from which it can be extendedtoward the direction M3 of the pre-aligner 25. As it is, the arm isagain extended so as to place the mask held by the arm onto thepre-aligner 25. The arm, after having received the mask from thepre-aligner through the course inverse to that described above, isfurther rotated and stopped at a position (M4 orientation) in which thearm is allowed to be extended toward the second loading chamber 41,where it is extended so as to hand over the mask to a mask receiver 47within the second loading chamber 41. It is to be noted that in case ofgripping the mask mechanically, a circumferential edge region (a rangewithin about 5 mm from the circumferential edge) of the mask should begripped. This is because the mask is entirely patterned (circuit wiringis formed) only excluding the circumferential edge region, gripping ofthe mask in that patterned region could cause a break or defective partof the pattern.

[0113] Since the second transport unit 63 has basically the samestructure as the first transport unit, only excluding that the transferoperation of the mask is performed between the mask rack 47 and theloading surface of the sample table, therefore the detailed descriptionshould be omitted.

[0114] In the loader 60, the first and the second transport units 61 and63 carry out the transfer operation of the mask as it is held in thehorizontal state from the cassette held by the cassette holder onto thesample table 50 located within the working chamber 31 and vice versa,wherein the up and down motions of the arms of the transport units arelimited only to the steps where the mask is taken out of and insertedinto the cassette, where the mask is placed on and taken out of the maskrack, and where the mask is placed on and taken out of the sample table.Therefore, even the transfer of such a large mask having a 30 cmdiameter, for example, can be carried out smoothly.

[0115] Transfer Operation of the Mask

[0116] The transfer operations of the mask from the cassette c carriedby the cassette holder onto the sample table 50 located in the workingchamber 31 will now be described sequentially.

[0117] As for the cassette holder 10, a suitable structure may beselectively employed therefor, as already set forth, depending on theparticular cases including one for the manual setting of the cassetteand another for the automatic setting of the cassette. In thisembodiment, once the cassette c is set on the elevating table 11 of thecassette holder 10, the elevating table 11 is lowered by the elevatingmechanism 12 and the cassette c is aligned with the access port 225.

[0118] When the cassette is aligned with the access port 225, the cover(not shown) arranged in the cassette is opened, and at the same time, acylindrical cover is disposed between the cassette c and the access port225 of the mini-environment unit so as to block the interior of thecassette and the space inside of the min-environment unit from theexternal environment. Since known structures may be used for the cover,and the detailed description of their structures and operations shouldbe omitted. It is to be noted that in the case where the shutter systemfor opening and closing the access port 225 is arranged in themini-environment unit 20 side, that shutter system should be actuated toopen the access port 225.

[0119] On one hand, the arm 612 of the transport unit 61 has beenstopped as it is oriented to either of the direction M1 or M2 (thedirection of M1, in this illustration), wherein when the access port 225is opened, the arm is extended to receive one of the masks accommodatedin the cassette by its tip portion. It is to be noted that the positionadjustment between the arm and the mask to be taken out of the cassettehas been executed by the up and down motions of the driving section 611and the arm 612 of the first transport unit 61 in this embodiment, andwithout any trouble, it may be executed by the up and down motions ofthe elevating table of the cassette holder or by both of them.

[0120] Once the receiving operation of the mask by the arm 612 iscompleted, the arm is contracted and the shutter system is actuated toclose the access port (with the shutter system installed therein), andthen the arm 612 is rotated around the axial line O₁-O₁ and ready to beextended toward the direction M3. As it is, the arm is extended andplaces the mask loaded on its tip portion or gripped by the chuck ontothe pre-aligner 25, which in turn determine the orientation of therotational direction (i.e., the direction around the central axis lineorthogonal to the mask plane) of the mask to be set within a specifiedrange. Once the aligning operation has been completed, the transportunit 61, after having received the mask from the pre-aligner 25 onto thetip portion of the arm, contracts its arm and takes a posture ready toextend the arm toward the direction M4. Then, the door 272 of theshutter system 27 is moved to open the access ports 226 and 436, so thatthe arm 612 is extended and loads the mask into the upper step side orthe lower step side of the mask rack 47 within the first loading chamber41. It is to be noted that as described above, before the shutter system27 goes into the open position to allow the mask to be transferred tothe mask rack 47, the opening 435 defined in the partition wall 434 isclosed to be airtight by the door 461 of the shutter system 46.

[0121] In the course of transfer operation of the mask by the firsttransport unit, as described above, a clean air flows down in a laminarflow (as the down flow) from the gas supply unit 231 arranged in theupper side of the housing of the mini-environment unit so as to preventthe dust from adhering to the top surface of the mask during itstransfer operation. A portion of the air in the surrounding of thetransport unit (in this embodiment, about 20% of the air supplied fromthe supply unit, mainly a contaminated air) is sucked through thesuction duct 241 and exhausted to the outside of the housing. Remainingportion of the air is recovered via the recovery duct 232 disposed inthe bottom of the housing and returned back to the gas supply unit 231.

[0122] Once the mask has been loaded in the mask rack 47 within thefirst loading chamber 41 of the loader housing 40 by the first transportunit 61, the shutter system 27 is actuated into the closed position toenclose the loading chamber 41. As it is, the first loading chamber 41is filled with an inactive gas to purge the air, and after that theinactive gas is also exhausted to bring the interior of the loadingchamber 41 into the vacuum atmosphere. The vacuum atmosphere, of thefirst loading chamber may be set at a low vacuum level. Once a certaindegree of vacuum has been obtained in the vacuum chamber 41, the shuttersystem 46 is actuated to open the access port 434, which has been closedto be airtight by the door 461, and the arm 632 of the second transportunit 63 is extended and receives one piece of mask from the maskreceiver 47 using the gripping device located in the tip portion thereof(with the mask loaded on the tip portion or gripped by the chuckattached to the tip portion). After the receiving operation of the maskhaving been completed, the arm is contracted, and the shutter system 47is again actuated to close the access port 435 by the door 461. It is tobe noted that before the shutter system 46 is actuated to open the door461, the arm 632 takes a posture ready to extend toward the direction N1of the mask rack 47. Further, as set forth before, prior to the openingoperation of the shutter system 46, the access ports 437 and 325 havebeen closed by the door 452 of the shutter system 45 to block thecommunication between the interior of the second loading chamber 42 andthe interior of the working chamber 31 in the airtight condition, andthe second loading chamber 42 is vacuum evacuated.

[0123] When the shutter system 46 has closed the access port 435, thesecond loading chamber is again vacuum evacuated and ultimately broughtinto the vacuum at a higher vacuum level than that in the first loadingchamber. During this period, the arm of the second transport unit 63 isrotated to a position in which it is allowed to extend toward the sampletable 50 of the working chamber 31. On one hand, in the sample tablewithin the working chamber 31, the Y table 52 is moved in the upwarddirection in FIG. 2 until the centerline X₀-X₀ of the X table 53 comesinto alignment with the X-axis line X₁-X₁ crossing the rotational axialline O₂-O₂ of the second transport unit 63, while at the same time the Xtable 53 is moved to a position closest to the leftmost position in FIG.2 and stands by in this state. When the second loading chamber has beenbrought into the approximately same level of vacuum condition as theworking chamber, the door 452 of the shutter system 45 is actuated toopen the access ports 437, 325, and the arm is extended so that the tipportion of the arm holding the mask comes near to the sample table ofthe working chamber 31. Then, the mask is loaded on the loading surface551 of the sample table 50. When the loading operation of the mask hasbeen completed, the arm is contracted, and the shutter system 45 closesthe access ports 437 and 325.

[0124] In the above description, the steps of operation to be takenuntil the mask in the cassette c is successfully transferred onto thesample table has been explained, and in order to return the mask thathas been loaded on the sample table and finished with the process backinto the cassette c, the above-described steps should be performed inthe inverse sequence for returning operation. Further, in order to keepa plurality of masks carried in the mask rack 47, during the masktransfer operation between the mask rack and the sample table by thesecond transport unit, the transfer operation of the mask may be carriedout between the cassette and the mask rack by the first transport unit,thereby allowing the inspection process to be carried out moreefficiently.

[0125] Specifically, if the mask rack 47 of the second transport unitcontains both the already-processed mask “A” and unprocessed mask “B”,

[0126] (1) at first, the unprocessed mask B is transferred to the sampletable 50, and the processing is started; and

[0127] (2) during this processing, the processed mask A is transferredfrom the sample table 50 to the mask rack 47 by the arm, and theunprocessed mask C is picked up from the mask rack similarly by the arm,properly aligned by the pre-aligner and then transferred to the maskrack 47 of the loading chamber 41.

[0128] Through this operation, during processing of the mask B, thealready-processed mask A can be replaced with the unprocessed mask C inthe mask rack 47.

[0129] Further, depending on the application of such an apparatus forproviding an inspection and/or an evaluation, a plurality of sampletables 50 may be arranged in parallel, in which the mask is transferredfrom a single mask rack 47 to each one of the tables, thereby enabling aplurality of masks to be similarly processed in parallel.

[0130]FIG. 6 shows a variation 30 b of a method for supporting a mainhousing. In the variation illustrated in FIG. 6, a housing main body 32b and a loader housing 40 b are suspended from a frame structure 336 bof a housing supporting device 33 b so as to be supported thereby.Bottom ends of a plurality of vertical frames 337 b secured to the framestructure 336 b are fixed to four corners of a bottom wall 321 b of thehousing main body 32 b respectively so as to support circumferentialwalls and a top wall by that bottom wall. In addition, a vibrationisolation device 37 b is disposed between the frame structure 336 b anda table frame 36 b. Further, a loader housing 40 is galso suspended by asuspender member 49 b fixed to the frame structure 336 b. In thevariation of the housing body 32 b illustrated in FIG. 6, since thecomponents are supported in a suspended manner, therefore the center ofgravity of entire unit including the main housing and many differentdevices provided therein can be kept low. In the supporting systems forthe main housing and the loader housing including the variation, eachsystem is designed to prevent the vibration from the floor from beingtransmitted to the main housing and the loader housing.

[0131] According to another variation, though not shown, only thehousing main body of the main housing is supported from the under sideby the housing supporting device, but the loader housing may be mountedon the floor in the same manner as that used for the mini-environmentunit. Further, according to still another variation, though not shown,only the housing main body of the main housing is suspended from theframe structure to be supported thereby, but the loader housing may bemounted on the floor in the same manner as that used for themini-environment unit.

[0132] According to the above embodiments, the following effects couldbe expected.

[0133] (a) An entire configuration of an inspection apparatus for animage projecting method using an electron beam can be obtained, in whicha subject to be inspected can be processed with a high throughput.

[0134] (b) Since the flow of clean air is supplied over the subject tobe inspected within the space of the mini-environment unit to preventthe dust adhesion and also the sensor is provided therein for observingthe cleanliness of the space, the inspection of the subject can becarried on while monitoring the dust in the space.

[0135] (c) Since the loading chamber and the working chamber aresupported collectively via the vibration isolation device, therefore thesupply of the subject onto the sample table and the inspection thereofcan be carried out without any effects from the external environment.

[0136] Electron Beam System

[0137] A detailed embodiment of the electron beam system 70 (see FIGS. 1and 6) disposed in the main housing 30 or 30 b is shown in FIG. 7.Referring to FIG. 7, an irradiating optical system 710 equipped with anelectron gun 711 for irradiating a mask M, such as a stencil mask 800,prepared as a sample is arranged in a lower side, and above thisirradiating optical system 710 is located the stencil mask 800 loaded onthe sample table 50, above which the a detector 770 for detecting anelectron beam passed through this stencil mask is located. Anembodiment, which will be described below, represents an embodiment inwhich the electron beam is irradiated upward from the electron gun 711located in the lower portion. It is a matter of course that analternative embodiment, in which the electron gun is arranged in anupper location and the electron beam is irradiated downward, may also beemployed.

[0138] As an electron gun is used a thermionic emission type of electrongun 711 which is activated to emit electrons by heating an electronemission material (cathode) 711 a. Lanthanum hexaboride (LaB₆) isemployed as the electron emission material (emitter) serving as thecathode. Any other materials may be used as far as they have a highfusion point (a low vapor pressure at high temperature) as well as asmall work function. In this illustrated embodiment, the electron gun711 comprises a single-crystal LaB₆ cathode 711 a having a tip of such asmall radius of curvature as 15 μmR, which is operative under aspace-charge-limited condition, thereby allowing the electron beamhaving a higher intensity and a lower shot noise to be emitted.

[0139] Further, by setting a distance between the Wehnelt 711 b and ananode 711 c to be equal to or longer than 8 mm and additionallydetermining a condition of the electron gun current to achieve a highbrightness, then the brightness can reach to a value greater thanLangmuir limit.

[0140] In this context, preferably the electron gun 711 in thisembodiment comprises the thermionic emission cathode 711 a and isoperable under the space-charge-limited condition. Alternatively, suchan electron gun 711 with a small electron source image having an FE(Field Emitter), a TFE (Thermal Field Emitter) or a Schottky cathode maybe used as the electron gun 711. It is to be noted that the“space-charge-limited condition” refers to such a condition that thecathode temperature is increased higher than a certain temperature wherean emission amount of the electron beam is less susceptible to theeffect from the cathode temperature.

[0141] A first shaping aperture 713 and a first electron lens 715 aredisposed along the direction of the irradiation of the electron gun 711(in the upward direction in the drawing). The first electron lens 715focuses an image of the electron beam that has passed through the firstshaping aperture 713 onto a second shaping aperture 719 (which will bedescribed later). A first deflector 717 is arranged in a location abovethe first electron lens 715 so as to surround an irradiation path of theelectron beam. In addition, above the first deflector 717, the secondshaping aperture 719, a first condenser lens 721 and a third shapingaperture 723 are disposed in this order, and also a second deflector 725is arranged surrounding the third shaping aperture 723.

[0142] The electron beam emitted from the electron gun 711 forms avariable shaped beam that has been configured into a desired shape bypassing through the first shaping aperture 713 and the second shapingaperture 719, which in turn irradiates an area at a certain moment inthe region to be inspected on the stencil mask 800. To explain this morespecifically, the electron beam that has passed through the firstshaping aperture 713 is deflected by the deflector 717, thereby changingthe irradiating position to the second shaping aperture 719, thusenabling the electron beam to be formed into the desired shape.Specifically, it is preferable to allow an elongated rectangular shapeof electron beam having a predetermined area to be formed. However, asquare shape of the electron beam may also be formed.

[0143] Thus in the present embodiment, the irradiation area can beadjusted by tuning the first deflector 717, and alternatively the firstand second shaping apertures 713 and 719 may be substituted with aplurality of apertures of different size so as to adjust the irradiationarea mechanically.

[0144] It is to be noted that the Koehler illumination system has beenemployed in the drawing as a system for illuminating the mask, andwithout any trouble, the critical illumination system may also beemployed therefor.

[0145] As described above, preferably the irradiating optical system 710of the present embodiment comprises at least one shaping aperture 713,719 and is designed such that the image of the shaping aperture isformed on the surface of the stencil mask 800. Further, it is alsopreferable that a plurality of such shaping apertures 713, 719 isprovided in the vicinity of an optical axis 801, wherein the area ofirradiation on the stencil mask 800 prepared as the sample is madevariable by changing the overlap between those shaping apertures 713,719.

[0146] The above-described third shaping aperture 723 serves forimproving a collimation of the electron beam illuminating the stencilmask 800, and accordingly the crossover image formed by the electron gun711 is focused on this third shaping aperture 723. The second deflector725 serving as the scanning means is a deflector required in such asituation where a main field of view is virtually divided, theillumination area is scanned in a step-and-repeat manner orcontinuously, and an image field curvature aberration and an astigmatismof the optical system after the transmission through the stencil mask800 should be compensated for in response to a position of the scanning.To explain this point in more detail, the second deflector 725 scans aposition of the electron beam on the mask in the step-and-repeat manneror continuously. For example, a primary electron beam is controlled tomake a scanning motion in the +X direction and −X direction by thesecond deflector 725. In this case, the sample table 50 carrying themask 800 is displaced in the +Y direction and −Y direction. By way ofthis, the mask 88 can be scanned entirely. In order to compensate forthe field curvature aberration and the astigmatism, a condition of avoltage to be applied to the doublet lens 731 (the electron lenses 731a, 731 b located downstream to the mask 800) should be changed inresponse to the position of the electron beam. For example, in order tocompensate for the field curvature aberration, when the electron beam ison the optical axis, the voltage to be applied to the lens is increasedto make a focal length shorter, and when the electron beam is away fromthe optical axis, the voltage to be applied to the lens is decreased tomake the focal length longer.

[0147] The second deflector 725, even if it is not used for applyingabove compensation, still can be used to scan across the surface of thestencil mask 800 and obtain its SEM image, thus carrying out theregistration. For providing such a registration, preferably the detector727 is provided in the electron gun 711 side of the stencil mask 800, sothat secondary electrons which are emanated by the impingement of theelectron beam (in other words, the primary electron beam) to the stencilmask 800 or back-scattered electrons which are reflected therefrom canbe detected by the detector 727.

[0148] It is to be noted that alternatively the crossover image of smalldiameter may be formed on the sample surface of the stencil mask 800 soas to scan it by changing the focal length of either one of thedifferent lenses (715, 721). Still in another alternative way, theoverlapped area between the first and the second shaping apertures (713,719) may be reduced to form an electron beam having a smaller diameter,and thus formed electron beam may be used to carry out the scanning aswell as the registration.

[0149] Preferably, the irradiation area of the electron beam irradiatingthe stencil mask 800 of the sample after having passed through the abovedescribed shaping apertures 713 and 719 may be formed in an elongatedrectangular shape having long sides and short sides. Herein, the seconddeflector 725 is involved in displacing the irradiation area in thedirection of the long sides, and the sample table 50 is moved in thedirection of the short sides to thereby carry out a serial displacementof the irradiation area in the direction of short sides. Since theinspection is carried out while moving the sample table continuously,the inspection can be achieved with high throughput even with a narrowfield of view.

[0150] The electron beam irradiating the stencil mask 800 (its mainbeams are represented by B1, B2 and B3 in the drawing) may be controlledto make a scanning operation in the step-by-step manner or continuously.

[0151] The first doublet lens 731 is disposed in a location above, or inother words downstream of the stencil mask 800, wherein the firstdoublet lens 731 comprises two electron lenses 731 a and 731 b. An NAaperture 733 is disposed between two lenses of the first doublet lens731. A second doublet lens 735 is disposed above the first doublet lens731, and further a detector 770 is disposed downstream to the seconddoublet lens 735.

[0152] The second doublet lens 735 consists of two electron lenses 735 aand 735 b.

[0153] The electron beam having passed through the stencil mask 800expands at an angle (clarified as the code α in the drawing)corresponding to the angular aperture α′ of the irradiation and entersthe first doublet lens 731. At that time, the electrons scattered at theside face of the stencil mask 800 are removed by the NA aperture 733.Further, for the inspection of the mask having a pattern formed on athin membrane, such as an X-ray mask, there is an effect inherent tothis NA aperture that can remove the electron beam that has beenscattered at a large angle on the membrane. After having passed throughthe first doublet lens 731, a transmission image of the stencil mask isformed. An area where this transmission image is formed is representedas a transmission image forming area 737. The formed transmission imageis further magnified by the second doublet lens 735 and irradiated ontothe detector 770.

[0154] The detector 770 comprises a MCP (Multi-Channel Plate) 771 and aFOP (Fiber Optical Plate) 775 as an irradiation lens system. The MCP 771is followed by the FOP 775 along the direction of the irradiation of theelectron beam (in the upward direction in the drawing). The detector 770further comprises a vacuum window 777 as the irradiation lens system, anoptical lens 779 as a relay optical system and a TDI detector 781 as adetection sensor having a plurality of pixels. The transmission image ofthe stencil mask magnified by the second doublet lens 735 is irradiatedto the MCP 771 as magnified by about 1,000 times, and accordingly thismagnified image by about 1,000 time is formed on the MCP 771. Thismagnified image is multiplied at the MCP 771, and the electron beamforming the image thus multiplied by the MCP 771 is converted into animage of light by a scintillator applied on a sample side surface of theFOP 775. This image is taken out of the atmosphere through the vacuumwindow 777, reduced in scale by an optical lens 779 and formed into animage on the TDI detector 781. It is to be noted that in the formemploying the optical lens 779, the FOP may not necessarily be used.

[0155] According to the above-described configuration, the presentoptical system, in which the irradiation beam and the transmission beamdo not follow the common optical path, can improve significantly a blurof the transmission beam caused by the space charge effect, as comparedto the system in which the primary electron beam is emitted from thediagonally above direction and then deflected by using an E×B separatorso as to normally enter the sample, and the secondary electron beamfollows the optical path common with the incident optical path of theprimary electron beam. Since the electrons that has passed through thestencil mask contributes nearly 100% to the image forming, therefore asignal having a good S/N ratio can be obtained.

[0156] The electron beam system according to the present embodiment canbe used to detect a defect in the stencil mask 800 or the sample basedon the electrons detected by the detector 770.

[0157] As described above, in the present embodiment, the electron beamthat has passed through the sample is magnified by the electron lens(the doublet lens 731, 735), which is in turn detected by the detector770 having a plurality of pixels to thereby form the image of thesample. Further, the present embodiment is characterized in that theelectron beam irradiating the detector 770 has a good collimation, inwhich as a specific configuration to achieve this good property, the NAaperture 733 is disposed between the two lenses of the first doubletlens 731 in a location where the principal ray B1, B2 and B3 are crossedwith one another. Then, the electron beam having passed through this NAaperture 733 is irradiated onto the detector 770.

[0158] A preferred embodiment with the NA aperture 733 arranged thereinis specified in a form having two stages of doublet lens 731 and 735,and a single piece of shaping aperture (the second shaping aperture719), wherein the main electron beams (B1, B2, B3) exiting from theshaping aperture are irradiated in parallel against the sample (thestencil mask 800). Further, the irradiating optical system 710 has anentrance pupil for the MCP 771 and the vacuum window 775 as theirradiation lens system in the entrance pupil 723, and the electronsource image is formed in this entrance pupil 723.

[0159] In a preferred embodiment of the present invention, amagnification of the doublet lenses 731 and 737 may be made variable inresponse to the size of the irradiation area of the electron beam. Aspecific configuration for making the magnification variable can beimplemented in such forms that the doublet lens is exchanged, that in aset of doublet lens, a distance between the front lens and the rear lensis adjusted, or that a distance between the first doublet lens and thesecond doublet lens is adjusted.

[0160] As the detection sensor in the detector 770, a CCD detector (aCCD sensor) may be used, and it is also possible that the size of theimage to be created by the scintillator is adjusted by the optical lens779 and then thus adjusted image is formed on the CCD plane in the CCDdetector. Advantageously, using the CCD detector enables themanufacturing at a low cost.

[0161] A preferred configuration of the electron beam system in thepresent invention will now be described below.

[0162] (1) The electron gun 711 is disposed below the sample, while thedetector 770 is disposed above the sample.

[0163] (2) A plurality of magnifying lenses for magnifying the electronbeam is arranged between the electron gun 711 and the detector 770. Inthe above embodiment, two sets of doublets lens (731, 737) are arranged.Herein, the doublet lens should be used as the lens for magnifying theelectron beam having passed through the sample at first. In the aboveembodiment, the first doublet lens 731 serves as this lens. Because ofthis arrangement, a transverse chromatic aberration and distortion arecompensated for, thereby allowing the image with a reduced blur anddistortion to be obtained.

[0164] (3) In the detector 770, the MCP 771 and the scintillator formedon the sample side of the FOP 775 are disposed in the vacuum, and behindthem, the vacuum window 777, the optical lens 779 as the relay opticalsystem, and the detection sensor (the CCD detector, the TDI detector781) are arranged in this sequence.

[0165] (4) In the detector 770, the relay optical system and the CCDdetector, or the relay optical system and the TDI detector are disposedin the vacuum. Further, in the embodiment of the present invention, thewhole unit of the electron beam system or the whole unit of the detector770 may be disposed in the vacuum.

[0166] (5) As the detection sensor in the detector 770, the EB-CCDdetector or the EB-TDI detector may be employed.

[0167] (6) In the electron beam system, since the signals are receivedfrom a plurality of pixels simultaneously, even if each pixel iscontrolled to actuate at 100 KHz, an equivalent frequency of the systemis greater than 200 MHz as a result of simultaneous reception of thesignals from the 2000 pixels.

[0168] (7) In the one electron beam system, a plurality of irradiationoptical system 700 and a plurality of detectors 770 are provided, witheach irradiation system in association with each detector, so as todetect defects in the sample.

[0169] Variation of the Inspection Apparatus

[0170]FIG. 8 shows a general configuration of a defect inspectionapparatus according to a variation of the present invention.

[0171] This defect inspection apparatus represents an inspectionapparatus using the electron beam system 70 described above (FIG. 7).This inspection apparatus consists of a control section 1016 shown in aright hand side in FIG. 8 and the electron beam system 70 shown in theleft hand side in FIG. 8. Similarly to FIG. 7, the electron beam systemcomprises an irradiation optical system 710 including an electron gun711 for emitting an electron beam disposed in a lower portion, abovewhich a stencil mask 800 and a sample table 50 for carrying the mask aredisposed. The system further comprises doublet lenses 731 and 737 as amagnifying lens for magnifying the emitted electron beam and also adetector 770 disposed at the top-most location. Herein, this detector770 is connected to a control section 1016 which controls the entiresystem and also executes a process for detecting any defects in thestencil mask 800 based on an electron image detected by the detector770.

[0172] The detector 770 may have any arbitrary configuration as far asit can convert the formed electron image into a signal that can beprocessed in a subsequent step. For example, as shown in detail in FIG.9, the detector 770 may consist of a scintillator screen 772, a relayoptical system 773, and an image sensor 775 composed of a plurality ofCCD elements. The scintillator screen 772 emits light by electrons andthus converts the electrons to a light. The relay lens 773 guides thislight to the CCD image sensor 775, where the CCD image sensor 775converts an intensity distribution of electrons on the surface of thestencil mask 800 into an electric signal or digital image data for eachelement, which is in turn output to the control section 1016.

[0173] The control section 1016 may comprise a general purpose personalcomputer or the like, as shown in FIG. 8 by way of example. Thiscomputer comprises a control section main part 1014 for executing avariety of control and arithmetic operations according to a specifiedprogram, a CRT 1015 for indicating a result of the operation of the mainpart 1014, and an input section 1018, such as a key board or a mouse,for an operator to input a command, while without any trouble, thecontrol section 1016 may be composed of a hardware dedicated for thedefect inspection apparatus or a work station.

[0174] The control section main part 1014 may consist of a CPU, a RAM, aROM, a hard disk, a variety of substrate such as a video substrate andthe like. An electronic image storage area 1008 for storing the electricsignals received from the detector 770 or the digital image data of theelectron image that has passed through the stencil mask 800 is allocatedon a memory such as the RAM or the hard disk. Further, the hard diskincludes a reference image storage section 1013 for storing in advance areference image data of a normal sample (stencil mask) having no defect.Yet further, on the hard disk, in addition to the control program forcontrolling the entire defect inspection apparatus, there is stored andefect detection program 1009, which reads out the electron image datefrom the storage area 1008 and based on the image data, automaticallydetects a defect in the stencil mask 800 according to a specifiedalgorithm. This defect inspection program 1009, as will be described indetail later, has a function for executing a matching operation betweenthe reference image read out of the reference image storage section 1013and the actually detected electron beam image so as to automaticallydetect a defective area, wherein if it is determined that the defect isexisting, then a warning display is indicated for the operator. In thisstep, the electron image 1017 may be displayed on a display section ofthe CRT 1015.

[0175] Then, an operation of the defect inspection apparatus accordingto the above embodiment will now be described by taking a flow chartshown in FIGS. 10 to 12 as an example.

[0176] At first, as shown in a main routine of FIG. 10, the stencil mask800 or a subject of inspection is set on the sample table 50 (Step1300). This may be performed such that every one of a number of masksstored in the loader is set one by one onto the sample table 50automatically, as described above.

[0177] Then, a plurality of images of areas to be inspected, which areoverlapped partially with one on another while being displaced from oneanother on the XY plane of the stencil mask 800 surface, is obtainedseparately (Step 1304). The plurality of areas to be inspected, theimages of which should be taken, represents, for example, rectangularareas designated by the reference numeral 1032 a, 1032 b, . . . 1032 k,. . . on the mask inspection area 1034,as shown in FIG. 13, which areclearly shown to be partially overlapped but displaced from one anotheraround the inspection pattern 1030 of the mask. For example, as shown inFIG. 14, sixteen sets of images 1032 of the areas to be inspected (i.e.,the inspection subject image) may be obtained. Herein, in the imageshown in FIG. 14, a rectangular square box corresponds to one pixel (orpossibly a block unit larger than the pixel), and black painted squareboxes corresponds to an image portion of the pattern on the stencil mask800. The detailed description of this step 1304 will be provided laterwith reference to a flow chart of FIG. 11.

[0178] Subsequently, the plurality of image data of the areas to beinspected which have been obtained in Step 1304 are compares formatching respectively to the reference image data (pattern data) storedin the storage section 1013 (Step 1308 of FIG. 10), thereby determiningwhether or not a defect is existing on the mask inspection surfaceencompassed by the plurality of areas to be inspected. In this step,so-called matching operation between image data is executed, which willbe described in detail later with reference to a flow chart of FIG. 12.

[0179] If it is determined from the result of Step 1308 that the defectis existing in the mask inspection surface encompassed by the pluralityof areas to be inspected (Step 1312 positive determination), an alarm ofexistence of the defect is given to the operator (Step 1318). As for amethod for giving the alarm, for example, a message indicating theexistence of the defect may be displayed on the display section of theCRT 1015, and additionally an enlarged image of the pattern 1017including the defect may be displayed at the same time. Such a defectivemask should be removed out of a sample chamber 31 so as to be stored ina different storage from that for the masks having no defect (Step1319).

[0180] As a result of the comparing operation in Step 1308, if it isdetermined that there is no defect in the stencil mask 800 (Step 1312negative determination), it is further determined whether or not thereis still other areas to be inspected on the stencil mask 800 underinspection (Step 1314). If there is still left the areas to be inspected(Step 1314 positive determination), then the sample table 50 is drivento displace the stencil mask 800 so that other areas to be inspected arebrought into the irradiation area of the electron beam (Step 1316).After that, the process returns back to Step 1302, and the similaroperations are repeated to those other areas to be inspected.

[0181] If there is no area to be inspected left on the stencil mask 800(Step 1314 negative determination) or after the removing step of thedefective mask (Step 1319), it is determined whether or not the stencilmask 800 that is currently under inspection is the last mask, or whetheror not there is any un-inspected mask remaining in the loader, thoughnot shown (Step 1320). If it is not the last mask (Step 1320 negativedetermination), then already inspected mask is stored in a predeterminedstorage, and a new un-inspected mask is instead set on the sample table50 (Step 1322). After that, the process returns back to Step 1302, andthe similar operations are repeated on that mask. If that is the lastmask (Step 1320 positive determination), the already inspected mask isstored in the predetermined storage, thus completing whole course ofoperations.

[0182] Then, the process flow of Step 1304 will be described withreference to the flow chart of FIG. 11.

[0183] In FIG. 11, first of all, an image number “i” is set to aninitial value 1 (Step 1330). This image number is an identificationnumber that has been given to each one of a plurality of images of areasto be inspected in sequence. Then, the image position (X_(i), Y_(i)) isdetermined for the area to be inspected of the set image number i (Step1332). This image position is defined as a specific position within thearea for bounding the area to be inspected, for example, as a centrallocation of the area. Currently, i=1, indicating the image position of(X₁, Y₁), corresponds to the central location of the inspection area1032 a, for example, as shown in FIG. 13. All of the image positions forthe image areas to be inspected have been determined in advance, forexample, stored on the hard disk of the control section 1016 and areread out in Step 1332.

[0184] Subsequently, a certain potential is applied to the seconddeflector 725 so that the electron beam passing through the seconddeflector 725 (see FIG. 7) of the irradiation optical system 710 of FIG.8 can be irradiated onto the image area to be inspected at the imageposition (X_(i), Y_(i)) determined at Step 1332 (Step 1334 of FIG. 11).

[0185] Next, the electron beam is emitted from the electron gun 711 andirradiated onto the surface of the set stencil mask 800 (Step 1336). Atthat time, the electron beam is deflected by an electric field generatedby the second deflector 725 and irradiated over the entire image area tobe inspected at the image position (X_(i), Y_(i)) on the mask inspectionsurface 1034. If i=1, the area to be inspected is represented by 1032 a.

[0186] The electron beam having passed through the stencil mask 800 isformed into an image on the detector 770 with a predeterminedmagnification by the double lenses 731 and 737. The detector 770 detectsthe imaged electron beam, converts it into the electric signal or thedigital image data for each detector element, and outputs thus convertedsignal or data (Step 1338). Then, the detected digital image data of theimage number i is transferred to the electronic image storage area 1008(Step 1340).

[0187] Subsequently, the image number i is incremented by 1 (Step 1342),and it is determined whether or not the incremented image number (i+1)is greater than a predetermined constant value i_(MAX) (Step 1344). Thisi_(MAX) represents the number of inspection images to be obtained, whichis “16” in the illustrated example of FIG. 14.

[0188] If the image number i is not greater than i_(MAX) (Step 1344negative determination), then the process returns back to Step 1332again, and the image position (X_(i+1), Y_(i+1)) is again determined forthe incremented image number (i+1). This image position defines aposition moved from the image position (X_(i), Y_(i)) determined at theprevious routine by predetermined distance (ΔX_(i), ΔY_(i)) in the Xdirection and/or the Y direction. In the example of FIG. 13, theinspection area corresponding to the incremented image number is locatedon the position (X₂, Y₂) moved from the inspection area (X₁, Y₁) only inthe Y direction, defining a rectangular area 1032 b indicated by thebroken line. It is to be noted that a value of (ΔX_(i), ΔY_(i)) (i=1, 2,. . . i_(MAX)) may have been determined appropriately based on the dataindicating empirically how much the pattern 1030 of the mask inspectionsurface 1034 is actually displaced from the field of view of thedetector 770 as well as based on the number and area of the inspectionareas.

[0189] Accordingly, the operations defined in Step 1332 through Step1342 are sequentially repeated on the i_(MAX) pieces of the inspectionareas. Those inspection areas are displaced in a partially overlappedmanner on the inspection surface 1034 of the stencil mask 800 so thatthe image position after the “k” times of displacement (X_(k), Y_(k))defines the image area to be inspected 1032 k, as shown in FIG. 13. Inthis way, 16 pieces of the image data to be inspected as illustrated inFIG. 14 by way of example is obtained in the image storage area 1008. Aplurality of obtained images of the areas to be inspected 1032 (theimages to be inspected) are shown to include a part or the entirety ofthe image 1030 a of the pattern 1030 on the mask inspection surface1034, as exemplarily illustrated in FIG. 14.

[0190] If the incremented image number i is greater than i_(MAX) (Step1344 positive determination), the process exits from this sub-routineand returns back to the comparing step (Step 1308) of the main routineof FIG. 10.

[0191] It is to be noted that the image data that has been transferredto the memory in Step 1340 consists of an intensity value of electronfor each pixel (so-called raw data) detected by the detector 770, andthese data may be processed with a variety of arithmetic operations andstored in the storage area 1008 allowing for the matching operation withthe reference image in the subsequent comparing step (Step 1308 of FIG.10). Such an arithmetic operation includes, for example, a normalizingoperation for making the size and/or density of the image date matchedto the size and/or density of the reference image data, as well as theoperation for removing a group of isolated pixels under the thresholdpixel number as the noise. Further, the data may be compressed andconverted into a feature matrix having features of the detected patternextracted within an allowable range not to degrade the precision ofdetection of a highly sophisticated pattern, rather than left as thesimple raw data. Such a feature matrix includes, for example, an m×nfeature matrix, in which a two-dimensional area to be inspectedconsisting of M×N pixels is divided into m×n (m<M, n<N) blockscomprising matrix components each made up of a sum of intensity valuesof secondary electrons of the pixels included in respective blocks (or anormalized value determined from the sum divided by a total number ofpixels in the entire area to be inspected). In this case, the referenceimage data should also be stored in the same form of representation asthat. The image data referred to in the embodiment of the presentinvention includes not only the simple raw data but also the image dataprocessed with a feature extraction by using a desired algorithm in sucha way as described above.

[0192] Next, the flow of the process of Step 1308 will be described inaccordance with the flow chart of FIG. 12.

[0193] First of all, the CPU of the control section 1016 reads thereference image data from the reference image storage section 1013 (FIG.8) onto a working memory such as the RAM (Step 1350). This referenceimage is indicated by reference numeral 1036 in FIG. 14. Then, the imagenumber i is reset to 1 (Step 1352), and the image data to be inspectedfor the image number i is read out of the storage area 1008 onto theworking memory (Step 1354).

[0194] Then, the read-out reference image data is matched with the datafor the image i, and the distance value D_(i) between both data iscalculated (Step 1356). This distance value D_(i) represents asimilarity between the reference image and the image i to be inspected,wherein a larger distance value indicates a greater difference betweenthe reference image and the image to be inspected. As for this distancevalue D_(i), any quantities so far as they can indicate the similaritymay be employed. For example, for the case where the image datacomprises the M×N of pixels, the secondary electron intensity (or thefeature quantity) of each pixel may be considered as an each positionvector component in an M×N dimensional space, and in that case,Euclidean distance or a correlation coefficient between the referenceimage vector and the image i vector in this M×N dimensional space may becalculated. It is a matter of course, the distance other than theEuclidean distance, for example, so-called urban area distance may becalculated. Further, from the fact that with the greater number ofpixel, the scale of the arithmetic operation will be enormous, it wouldbe rather preferable to calculate the distance between the image datasets represented by the m×n feature vector as mentioned above.

[0195] Subsequently, it is determined whether or not the calculateddistance value D_(i) is smaller than the predetermined threshold value“Th” (Step 1358). This threshold value Th may be experimentallydetermined as a reference for determining a sufficient match between thereference image and the inspected image.

[0196] If the distance value D_(i) is smaller than the threshold valueTh (Step 1358 positive determination), it is determined that theinspected area of interest 1034 on the stencil mask 800 has “no defect”(Step 1360), and the process exits from the present sub-routine toreturn back. Specifically, if at least one image among the inspectedimages that is approximately identical with the reference image isencountered, it is determined that there is “no defect”. In this way,since there is no need to make the matching operation with every one ofthe inspected images, a quick determination will be feasible. In thecase of FIG. 14, it is obvious that the inspected image defined at row 3and column 3 is approximately identical with the reference image withoutdisplacement relative to the reference image.

[0197] If the distance value D_(i) is greater than the threshold valueTh (Step 1358 negative determination), the image number i is incrementedby 1 and the image number (i+1) is defined as new image number i, (Step1362), and then it is determined whether or not the new image number iis over a certain value i_(MAX) (Step 1364).

[0198] If the new image number i is not greater than i_(MAX) (Step 1364negative determination), the process returns to Step 1354 to read theimage data for the new image number i, and the similar operations arerepeated.

[0199] If the image number i is greater than i_(MAX) (Step 1364 positivedetermination), it is determined that there is “a defect existing” onthe inspected area of interest 1034 of the mask (Step 1366), and theprocess exits from the present sub-routine to return back. That is, ifany one of the inspected images is not approximately identical with thereference image, it is determined that there is “a defect existing”.

[0200] Preferred embodiments of the sample table according to thepresent invention have been described, and it is to be understood thatthey are not limited to those described above, but may be modifiedwithin the scope and spirit of the present invention.

[0201] For example, although the stencil mask has been taken by way ofexample as a sample to be inspected, the sample to be inspected in thepresent invention is not limited to this, but any objects a defect ofwhich can be detected by applying the electron beam may be selected asthe sample to be inspected.

[0202] Further, the present invention is also applicable to a device forcarrying out a defect inspection by using a beam of charged particlesother than the electrons and in addition, to any devices capable ofobtaining an image by which the sample can be inspected for a defect.

[0203] Further, although in the above embodiment, in carrying out thematching operation between the image data, either one of the matchingbetween the pixels and the matching between the feature vectors has beenused, the both of them may be used in combination. Both of the quick andthe highly precise operations can be accomplished together throughtwo-steps of processing comprising, for example, a first step forapplying a quick matching operation with the feature vector requiringless operational volume and a second step for applying another matchingoperation with more detailed image data to the resultant inspectionimage having higher similarity from the first step.

[0204] Further, although in the embodiment of the present invention, thedisplacement of the image to be inspected has been dealt with only byoffsetting the position of the irradiation area of the electron beam,such a process of searching for an optimal matching area on the imagedata before or during the matching operation (for example, by detectingareas having a higher correlation coefficient for matching) may becombined with the present invention. With this combination, since agreater scale of displacement of the inspected image can be dealt withby offsetting the irradiation area of the primary electron beamaccording to the present invention and a relatively smaller scale of thedisplacement can be absorbed by a subsequent step of digital imageprocessing, therefore the precision of the defect inspection can beimproved.

[0205] Also, the flow of the flowchart of FIG. 10 is not limited to theillustrated one. For example, although once having been determined thatthe sample has a defect in Step 1312, further defect inspection for theother areas on that sample is not applied thereto, the flow of processmay be modified such that the entire area on the sample may be inspectedfor the defect. Further, if the irradiation area of the electron beammay be expanded so as to cover substantially the entire area to beinspected on the sample by one-time of irradiation, Step 1314 and Step1316 may be omitted.

[0206] As having described above in detail, according to the defectinspection apparatus of the present embodiment, since the sample can beinspected for any defect by obtaining each of a plurality of images ofthe areas to be inspected which are overlapped partially with one onanother while being displaced from one another on the sample and thencomparing those images of the area to be inspected with the referenceimage, therefore such an excellent effect is obtained that thedegradation of the precision in defect inspection otherwise caused bythe offset between the image to be inspected and the reference image canbe prevented.

[0207] Further, according to a device manufacturing method of thepresent invention, since the defect inspection apparatus as describedabove is used to provide a defect inspection of the mask, such anexcellent effect can be obtained that the yield of the products can beimproved and any defective products can be prevented from being shipped.

[0208] Embodiment of an Electron Beam System

[0209]FIG. 15A shows an embodiment of a stencil mask inspectionapparatus of single beam type. An electron beam emitted from an electrongun 711 is converged by a condenser lens 751 and an objective lens 753and focused on a stencil mask 800, wherein deflectors 755 and 757control the electron beam to make a two-dimensional scanning motion overthe stencil mask 800. The electron beam having passed through anaperture of the stencil mask 800 is detected by an MCP 771, amplifiedand A/D converted by an amplifier 761 and formed into image data in animage forming circuit 763. This image data is compared with the designdata generated by a CAD, and a coordinate with a different data isoutput.

[0210] In this embodiment, for example, the deflectors 755 and 757control the single beam to make a scanning motion in the X-direction,and a sample table 50 is moved in the Y-direction. It is a matter ofcourse that the deflectors 755 and 757 may be used for the scan motionof the single beam in the Y-direction, while the sample table 50 may bemoved in the X-direction.

[0211]FIG. 15B shows an embodiment different from that shown in FIG. 15Ain that the former employs a plurality of electron beams. Electron beamsemitted from an electron gun 711′ comprising a L_(a)B₆ cathode aremagnified in the direction of emission by a condenser lens 752 so as tobe irradiated to a multi-aperture 756 arranged above a second condenserlens 754. The electron beams shaped by the multi-aperture 756 arefocused on a stencil mask 800 with the aid of a reduction lens 758 andan objective lens 760. The electron beams having passed through thestencil mask 800 are magnified by the magnifying lenses 762 and 764,detected by a plurality of detectors (respective detectors aredesignated by codes a˜f, collectively by 770′), and converted intodigital signals by A/D converters 768 associated with respectivedetectors to thereby provide a defect inspection process. With aplurality of optical axes for forming a multi-beam, an aberration may bereduced and each beam can be finely focused.

[0212] In the present embodiment, deflectors 755′ and 757′ are arrangedbetween the second condenser lens 754 and a reduction lens 758. Thedeflectors 755 and 757′ control the plurality of electron beams focusedon the stencil mask 800 so as to scan the stencil mask 800two-dimensionally. Also in the present embodiment, for example, thedeflectors 755′ and 757′ control the plurality of electron beams to makea scanning motion in the X-direction, and the sample table 50 is movedin the Y-direction. As a matter of course, the deflectors 755′ and 757′may control the plurality of electron beams to make a scanning motion inthe Y-direction, while the sample table 50 may be moved in theX-direction.

[0213] A cross section of each of the plurality of electron beams may becircular or rectangular. However, in the case of the plurality ofelectron beams being used for the X-direction scanning, preferably eachof the electron beams may be spaced equally from others in theX-direction.

[0214] According to the above embodiment, the following effect could beobtained.

[0215] 1. Since the irradiating electron beams is controlled to be goodat collimation, that is, an angular aperture a is made smaller,therefore an aberration of a magnifying optical system will be smallerto thereby obtain an image of high resolution.

[0216] 2. Since the irradiation optical system comprises a two-stage oflenses but constructs a telecentric optical system, therefore theoptical system may be made simple and further advantageously provides agreat allowance for variation in the Z-directional position of thesample. In addition, since the angular aperture a is small, a long focaldepth may be provided.

[0217] 3. Since the inspection is carried out while moving the sampletable continuously, a higher throughput of the inspection can beachieved even with a narrow main field of view.

[0218] 4. With a scanning motion within the main field of view in astepping or serial manner to thereby apply a dynamic aberrationcompensation, a low aberration can be achieved even with a larger a anda higher beam current.

[0219] 5. Since the magnification for focusing the scintillator image onthe CCD is tuned by the optical lens, there will be no need to adjustthe magnification of the primary optical system precisely.

[0220] 6. With a use of the L_(a)B₆ electron gun under high brightnesscondition or the FE electron gun, the high resolution as well as thehigh throughput may be achieved. The equivalent frequency per pixel over800 MHz is also possible.

[0221] 7. With an arrangement disposing the electron gun in a lowerlocation and the detector in a high location, the position of the maskis made lower to thereby improve a resistance against the vibration.

[0222] 8. With an arrangement employing a doublet lens as a first-stageof lens, the chromatic aberration caused by the magnification anddistortion can be compensated for and accordingly less blurred imagewith smaller distortion may be obtained.

[0223] 9. Since the magnification of the magnifying lens system is madevariable, the inspections to all types of character masks, including aone-to-one magnification mask, a ¼ magnification (reduction) mask, a{fraction (1/10)} magnification (reduction) mask, can be carried outefficiently.

[0224] 10. With the TDI detector placed in an outside of the atmosphere,a high speed signal can be handled easily.

[0225] 11. Since changing the lens conditions of the illumination systemcan provide a small beam with a reduced crossover, therefore theregistration may be carried out with high precision.

[0226] 12. Using the electron beam allows for the inspection with higherintensity than using the light. Owing to this, such a trouble to producedefective products may be reduced.

[0227] 13. Since the image data is compared with the pattern data, itcan be inspected whether or not the compensation has been appliedproperly as a result of proximity effect compensation.

[0228] Device Manufacturing Method

[0229] An embodiment of the semiconductor device manufacturing methodaccording to the present invention will now be described with referenceto FIGS. 16 and 17.

[0230]FIG. 16 is a flow chart illustrating one embodiment of thesemiconductor device manufacturing method according to the presentinvention. The manufacturing process in this embodiment includes thefollowing main processes.

[0231] (1) A wafer manufacturing process for manufacturing a wafer (orwafer preparing process for preparing a wafer) (Step 1400).

[0232] (2) A mask manufacturing process for fabricating a mask to beused in the exposure (or a mask preparing process) (Step 1401).

[0233] (2′) An inspection process of a fabricated mask (this step usesan inspection apparatus equipped with an electron beam system describedabove).

[0234] (3) A wafer processing process for performing any processingtreatments necessary for the wafer (Step 1402).

[0235] (4) A chip assembling process for cutting out those chips formedon the wafer one by one to make them operative (Step 1403).

[0236] (5) A chip inspection process for inspecting an assembled chip(Step 1404).

[0237] It is to be appreciated that each of those processes furthercomprises several sub-processes.

[0238] Among those main processes, one main process that gives acritical affection to the performance of the semiconductor device is (3)A wafer processing process. In this wafer processing process, thedesigned circuit patterns are deposited on the wafer one on another,thus to form many chips, which will function as memories or MPUs. Thiswafer processing process includes the following sub-processes.

[0239] (A) A thin film deposition process for forming a dielectric thinfilm to be used as an insulation layer, a metallic thin film to beformed into a wiring section or an electrode section, and the like (byusing the CVD process or the sputtering).

[0240] (B) An oxidizing process for oxidizing thus formed thin filmand/or the wafer substrate.

[0241] (C) A lithography process for forming a resist pattern by using amask (reticle) in order to selectively process the thin film layerand/or the wafer substrate.

[0242] As for the mask used in this lithography process, those masksthat have been inspected with the inspection apparatus as describedabove may be used.

[0243] (D) An etching process for processing the thin film layer and/orthe wafer substrate in accordance with the resist pattern (by using, forexample, the dry etching technology).

[0244] (E) An ions/impurities implant and diffusion process.

[0245] (F) A resist stripping process.

[0246] (G) An inspection process for inspecting the processed wafer.

[0247] It should be noted that the wafer processing process must becarried out repeatedly as desired depending on the number of layerscontained in the wafer, thus to manufacture the semiconductor devicethat will be able to operate as designed.

[0248]FIG. 17A is a flow chart illustrating the lithography processincluded as a core process in the wafer processing process of FIG. 16.The lithography process comprises the respective processes as describedbelow.

[0249] (a) A resist coating process for coating the wafer having acircuit pattern formed thereon in the preceding stage with the resist(Step 1500).

[0250] (b) An exposing process for exposing the resist (Step 1501).

[0251] (c) A developing process for developing the exposed resist toobtain the pattern of the resist (Step 1502).

[0252] (d) An annealing process for stabilizing the developed resistpattern (Step 1503).

[0253] Known procedures may be applied to all of the processes describedabove including semiconductor device manufacturing process, the waferprocessing process and the lithography process, and any furtherexplanation about those will not be needed.

[0254] When a defect inspection method, a defect inspection apparatusaccording to the present invention is used in the inspection process of(2)-(2′) and the lithography process described above, even a stencilmask having a fine pattern can be inspected with high throughput, sothat a total inspection can be employed to make it possible to preventany defective products from being produced.

[0255] Inspection Procedure

[0256] An inspection procedure in the above-described inspection processof (2)-(2′) will be described.

[0257] In general, since an inspection apparatus using an electron beamis expensive and a throughput thereof is rather lower as compared toother processing devices, therefore in the current circumstances theinspection apparatus is used after an important process (for example,after the process of etching, film deposition, CMP (Chemical-mechanicalpolishing) planarization or the like) where it is considered that theinspection is required most.

[0258] A mask to be inspected is, after having been positioned on anultra-precise X-Y stage through an atmospheric conveying system and avacuum conveying system, secured by an electrostatic chuck mechanism orthe like, to which a defect inspection and so on may be subsequentlycarried out in accordance with the procedure (shown in FIG. 17B). Firstof all, by using an optical microscope, a position check of each dieand/or a height detection of each location may be carried outappropriately as needed and those results may be stored. In addition tothose operations, the optical microscope is used also to acquire anoptical microscopic image for a desired location, such as a defectivelocation, which will be used for the comparison with electron beamimage. In next step, information of recipe corresponding to the type ofa mask (i.e., after which step the mask is currently is, and what themask size is, 20 cm or 30 cm, and so on) is input to the device, andafter a series of operations including a designation of the inspectionplace, a setting of the electronic optical system and a setting of theinspection condition, the defect inspection is applied typically at realtime while carrying on the acquisition of the images. Comparison amongcells and comparison among dies are performed by a high speedinformation processing system loaded with an algorithm thus to carry outthe inspection, and the results are output to the CRT and the like orstored in the memory as needed. The defect includes a particle defect,an abnormal shape (pattern defect) and an electric defect (break or badconduction of wirings or vias), which may be distinguished from oneanother and/or classified according to the size of defect or the degreeof defect including whether it being a killer defect (a fetal defectleading to a disabled chip) or not, automatically at real time. Thedetection of the electric defect can be achieved by detecting anabnormal contrast. For example, since the location of bad conduction isusually charged to be positive through the electron beam irradiation (inthe order of 500 eV) indicating degraded contrast, it can bedistinguished from a normal location. A means for the electron beamirradiation in this case is an electron beam generation means(generation means for thermion or UV/photoelectron) of low potential(energy) arranged separately from the electron beam irradiation meansused for a regular inspection, in order to enhance the contrast causedby the potential difference. Prior to the irradiation of the electronbeam for inspection onto the area to be inspected, this electron beam oflow potential (energy) is generated and irradiated. For the case of theimage projection system in which the positive charging is generated byirradiating the electron beam for inspection in itself, the additionalelectron beam generation means of low potential is not required to bearranged separately, depending on the specification. Further, applyingto a sample, such as a mask, a positive or a negative potential relativeto the reference potential also makes it possible to perform the defectdetection based on the difference in contrast (caused by the fact thatthe flowability is different depending on the forward direction or theinverse direction of the elements). This may be applicable to a linewidth measuring device and also to an alignment precision measurement.

[0259] As described above, according to the embodiment of the firstinvention, in which the electron beam is employed to form the image ofthe mask, more minute defects can be inspected for as compared to therelated defect inspection apparatus typically using the light.

[0260] Further, since the electron beam having passed through the maskis used to form the image of the sample, which means that theirradiation beam and the transmission beam would not follow the commonpath, the out-of-focus of the transmission beam otherwise caused by thespace charge effect can be improved significantly as compared to therelated device guiding the irradiation beam and the transmission beam tofollow the common path, and consequently the signal having a good S/Nratio can be obtained and also the defect of the sample can be detectedin a short time.

[0261] An embodiment according to the second invention will bedescribed.

[0262] An embodiment of the second invention relates to an apparatus forcarrying out a semiconductor processing process including the steps oflithography, film deposition (CVD, sputtering, plating), oxidation,impurities doping, etching, flattening, cleaning and drying of a samplesuch as a wafer or a stencil mask, and also for carrying out a featureobservation or a defect inspection of a high-density pattern in thesample such as the wafer or the stencil mask, which has been fabricatedthrough above process, with high precision and high reliability, andfurther to a semiconductor device manufacturing method for carrying outthe pattern inspection in the course of device manufacturing process byusing the apparatus.

[0263] The second invention further relates to an apparatus for carryingout a defect inspection of a mask used for a semiconductor devicemanufacturing.

[0264] Conventionally, respective units in the semiconductormanufacturing apparatus and the feature observation apparatus or thedefect inspection apparatus have been respectively fabricated asseparate and independent units (stand-alone units) and disposedseparately in a line. Because of this arrangement, it has been requiredthat a sample such as a wafer which has been finished with one of thesemiconductor processing processes should be placed in a cassette andtransferred by some transport means from one unit of the semiconductormanufacturing apparatus to the inspection apparatus directly or via acleaning/drying unit.

[0265] Further, in the related art system where the electron beam isused to inspect the stencil mask with high precision, a narrow electronbeam is emitted from the reverse side of the mask to scan it, and thetransmission electrons having passed through the sample are detected tothereby provide the inspection.

[0266] If the respective units (including devices) are arranged asdescribed above, the sample transport means are required betweenrespective units, and additionally each unit needs a loader means andunloader means for taking the sample in and out of the cassette.Consequently, there arises a problem including an extended area forinstalling the apparatus, an increase in a total cost of the apparatusand also an increase in a probability of contamination of the samplesuch as a wafer.

[0267] Besides, there has been another problem that the throughput willbe extremely small, because the narrow electron beam is used in theabove inspection of the mask.

[0268] The embodiment according to the second invention has been made tosolve the above problems, and an object thereof is to provide asemiconductor manufacturing apparatus that can reduce the area requiredfor installing the apparatus, reduce the total cost of the apparatus andfurther reduce the probability of the contamination of the sample tothereby improve the yield of the process by eliminating the transportmeans among respective units and sharing the loader means and unloadermeans among the respective units, and also to provide a device andmethod for carrying out the defect inspection of the stencil mask withhigh throughput.

[0269] Then, the summary of a semiconductor manufacturing apparatusaccording to the second invention will be described.

[0270] This semiconductor manufacturing apparatus is prepared for asample such as a wafer and characterized in incorporating a defectinspection apparatus.

[0271] Owing to the configuration of the semiconductor manufacturingapparatus integrated with the defect inspection apparatus therein, thesample, such as a wafer or a stencil mask, that has been taken in by theload section is transferred into the defect inspection apparatus withinthe apparatus after the completion of one manufacturing process, andthen taken out of the unload section after the inspection in the defectinspection apparatus. Accordingly, the number of pairs of the loadsection and the unload section corresponding to the number of units havebeen required so far, but according to this semiconductor manufacturingapparatus, the number of the pair of load and unload sections will bemade only one. Further, the transport unit of the sample such as a waferconventionally required between the semiconductor manufacturingapparatus and the defect inspection apparatus can be eliminated.Therefore, the floor area for installing the apparatus can be reduced,the total cost of the apparatuses can be reduced and further theprobability of the contamination of the sample such as a wafer can bereduced to thereby improve the yield of the process.

[0272] In the semiconductor manufacturing apparatus, the defectinspection apparatus may be an apparatus using an energy beam, and maybe integrated with the semiconductor manufacturing apparatus.

[0273] In the semiconductor manufacturing apparatus, the apparatus maycomprise an etching (pattern forming) section, a cleaning section, adrying section, an inspection section having the inspection apparatus,and the load and unload sections, wherein the inspection section may bedisposed in the proximity of either one or either two or three of theetching section, the drying section and the unload section.

[0274] According to this arrangement, the floor area for installing theentire apparatus can be reduced, and also four functions of the patternforming processing, the cleaning, the drying and the inspection can behandled within one unit, and further since the main components aredisposed closely to one another, advantageously the efficiency will beincreased and the floor area for installing the apparatus will bereduced.

[0275] In an alternative semiconductor manufacturing apparatus, theapparatus may comprise a plating section, a cleaning section, a dryingsection, an inspection section having the defect inspection apparatus,and load and unload sections, wherein the inspection section is disposedin the proximity of either one or either two or three of the platingsection, the drying section and the unload section. According to thisarrangement, the same effect can be obtained even in the plating unit asthat obtainable in the CMP.

[0276] In the semiconductor manufacturing apparatus, the defectinspection apparatus may be an electron beam inspection apparatus, andthe cleaning unit and the drying unit may be incorporated in thesemiconductor manufacturing apparatus.

[0277] According to this arrangement, the sample such as a stencil maskcan be inspected with higher resolution by the defect inspectionapparatus, which means that an inspection of a clear defect and anopaque defect may be feasible. Further, owing to the incorporation ofthe cleaning unit and the drying unit inside the apparatus, since theload and unload sections in association with the cleaning and dryingunit that have been conventionally installed as the stand-alone unit canbe eliminated and also the sample transport unit can be eliminated,therefore the floor area for installing the apparatus can be reduced,also the total cost of the apparatus can be reduced, and further theprobability of contamination of the sample such as a stencil mask can bereduced, thereby improving the yield of the process.

[0278] Alternatively, the above defect inspection apparatus may be adefect inspection apparatus using an energy beam, and the defectinspection apparatus may be integrated with the semiconductormanufacturing apparatus. The concept of an energy particle beam or theenergy beam includes an electron beam, an X-ray, an X-ray laser, anultra-violet ray, an ultra-violet ray laser, photoelectrons and thelight. Besides, the defect inspection apparatus using the energyparticle beam or energy beam may comprise at least an energy particleirradiation section, an energy particle detection section, aninformation processing section, an X-Y stage and a sample loading table.

[0279] In the semiconductor manufacturing apparatus, the electron beamdefect inspection apparatus may comprise a differential exhaustingsystem.

[0280] According to this configuration, there is no need to vacuumexhaust a space around the sample stage of the electron beam system, andaccordingly a load-lock mechanism to be disposed upstream and downstreamto that stage space can be eliminated thereby allowing for the samplesuch as a wafer to be transferred without any restriction.

[0281] In the semiconductor manufacturing apparatus, the electron beamirradiation area on the surface of the sample can be evacuated by thedifferential exhausting system.

[0282] According to this configuration, more efficient exhausting systemcan be constructed by exclusively exhausting the electron beamirradiation area on the sample surface.

[0283] In the semiconductor manufacturing apparatus, the defectinspection unit may be an electron beam defect inspection apparatus ofscanning-type electron microscope (SEM) system.

[0284] Further, in the semiconductor manufacturing apparatus, theprimary electron beam used in the electron beam defect inspectionapparatus may consist of a plurality of electron beams, in whichsecondary electrons from the sample are deflected from the optical axisof the primary electron beams by an E×B filter (Wien filter) so as to bedetected by a plurality of detectors.

[0285] In the semiconductor manufacturing apparatus, the defectinspection apparatus may be an electron beam defect inspection apparatusof image projection-type electron microscope system.

[0286] In the semiconductor manufacturing apparatus, the primaryelectron beam used in the electron beam defect inspection apparatus mayconsist of a plurality of electron beams, in which the plurality ofelectron beams are operatively irradiated onto the sample so as to scanthe surface thereof, and the secondary electrons from the sample aredeflected from the optical axis of the primary electron beam by the E×Bseparator (Wien filter) so as to be detected by a two-dimensional or aline image sensor.

[0287] With this configuration, a dosage of the electron beam and theresolution of the secondary optical system can be improved, and therebythe throughput thereof may also be improved.

[0288] Such an electron beam system representing the defect inspectionapparatus can be provided, in which the electron beam emitted from theLaB₆ electron gun is shaped properly and irradiated to the sample, andthe electron beam emanated from the sample is formed into an image by anoptical system of image projection-type electron microscope system,wherein the electron beam system may comprise a load-lock chamber forloading/unloading, and the LaB₆ electron gun may be operable in thespace-charge-limited condition.

[0289] In the electron beam system, the electron beam emanated from thesample may be back-scattered electrons or transmission electrons.

[0290] In the electron beam system, a image-projected sample image maybe converted to an optical image by a scintillator screen, and theoptical image may be formed on the TDI detector by the FOP or the lenssystem.

[0291] In the electron beam system, the image-projected sample image maybe formed on the TDI detector having sensibility to the electron beam.

[0292] In the electron beam system, the sample may be secured on thesample table by the electrostatic chuck, a laser interferometer formeasuring the position of the sample table may be provided, and thesample may also be secured within the load-lock chamber by theelectrostatic chuck.

[0293] The defect inspection apparatus may be used to inspect the waferin the course of processing. This may help improve the yield of theprocessing significantly.

[0294] An improved device manufacturing method can be provided, in whicha defect inspection and defect analysis of a wafer or a mask that hasbeen finished with one of the manufacturing processes is performed andthe result will be fed back to the flow of processes.

[0295] There will now be described in detail with reference to theattached drawings.

[0296]FIG. 18 is a schematic diagram illustrating a configuration of astencil mask forming (etching) apparatus 100″ with an inspection unitincorporated therein, which represents an example of the semiconductormanufacturing apparatus of the second invention. The apparatus comprisesas main components a load section 1″ equipped with a load unit 21″, anetching section 2″ equipped with a pattern forming unit 22″, a cleaningsection 3″ equipped with a cleaning unit 23″, a drying section 4″equipped with a drying unit 24″, an inspection section 5″ equipped withan inspection unit 25″ and an unload section 6″ equipped with an unloadunit 26″, all of which are arranged functionally so as to make up anintegrated unit. That is, FIG. 18 shows one example of the secondinvention comprising respective sections that have been disposedfunctionally. In addition, through not shown, transport mechanismsand/or alignment mechanisms for the sample such as a stencil mask may bedisposed in functionally desired spots, respectively. The load section1″ and the unload section 6″ are equipped with mini-environmentmechanisms (a mechanism for circulating the air or a gas such asnitrogen that has been cleaned by a cleaning unit in a down flow tothereby prevent the contamination of the sample such as a wafer),respectively, through not show. The sample transport mechanism isequipped with a vacuum chuck mechanism, an electrostatic chuck mechanismor a mechanical sample clamping mechanism, which are typically requiredfor fixedly securing the sample, while for simplicity such a componentis omitted in the drawing. There is no need to provide the load section1″ and the unload section 6″ independently, but they may be collectivelyprovided in the form of a single unit of transport mechanism withsingle-chamber. Generally, it is preferred that the load section 1″, theunload section 6″ and a control panel (not shown) may be arranged asillustrated in FIG. 18 so that they can be accessed (manipulated) fromone direction, thus achieving a through-the-wall system (in which thesample loading/unloading mechanism and the control section areexclusively located in a chamber having a higher cleanliness, while theunit main body that is more apt to produce dusts is located in a placeof lower cleanliness, with a partition wall disposed in spacetherebetween to define the interface, thereby reducing the load to thechamber having the higher cleanliness).

[0297]FIG. 19 shows an exemplary process flow of the second invention.The sample such as a wafer or a stencil mask is, as typicallyaccommodated in the cassette, conveyed from the preceding step 107″ tothe sample transport step 108″, taken out of the cassette in the loadsection 1″ and inserted into the etching section 2″ (the sample loadstep 101″), where a pattern forming processing is applied thereto (theetching step 102″), and then further transferred through the cleaningstep 103″ in the cleaning section 3″ and the drying step 104″ in thedrying section 4″ to the inspection section 5″. The sample is subjectedto a feature inspection and/or a defect inspection in the inspectionsection 5″ (the inspection step 105″), and transferred via the unloadsection 6″ into the cassette (the sample unload step 106″), and afterthat the sample is sent, as carried in the cassette, via the sampletransport step 108″ to a subsequent step 109″, for example, the step ofexposing process.

[0298] In the process flow of FIG. 19, the sample that do not need theinspection process 105″ is directly sent to the unload step 106″ afterthe cleaning and the drying steps without passing through the inspectionstep 105″, as indicated by the A line. Besides, similarly, the samplecan skip the etching step 102″, the cleaning step 103″ and the dryingstep 104″, as indicated by the B line.

[0299] In the related wafer processing process (shown in FIG. 20), thepattern forming step by the etching, the cleaning and the drying steps,and the inspection step have been performed respectively by eachindependent (stand-alone) etching unit 11″, cleaning and drying unit 12″and inspection unit 13″ (shown in FIG. 20). Since each one of thoseunits is equipped with the load section 1″ and the unload section 6″,meaning that 3 pairs of load section and unload section are arranged intotal. Further, the unit 108″ for transporting the samples has beeninstalled between respective units.

[0300]FIG. 21 shows a wafer processing process according to the relatedart. The sample such as a wafer is, as typically accommodated in thecassette, conveyed from the preceding step 107″ to the sample transportstep 108″, passed through the load section 1″ and inserted into theetching section 2″ (the sample load step 101″), where a flatteningprocess is applied thereto (the etching step 102″), and then transferredthrough the sample unload step 106″, the sample transport step 108″ andthe sample load step 101″, and after the cleaning step 103″ and thedrying step 104″, further transferred through the sample unload step106″ and the sample transport step 108″ into the inspection apparatus13″ (line C). The sample is passed through the load section 1″ (the loadstep 101″) to the inspection section 13″, where the feature inspectionand/or the defect inspection are applied thereto (the inspection step105″). After that, the sample is further transferred through the unloadsection 6″ of the inspection apparatus 13″ into the cassette (the sampleunload step 106″), and subsequently the sample is, as in the cassette,transferred by the sample transport step 108″ to a subsequent processingstep 109″, for example, the step of exposing process (line D).Typically, since the inspection process takes long time, not all of thewafers after the processes of etching, cleaning and drying areinspected, but the sampling inspection is applied. That is, most of themfollow the line indicated by E of FIG. 21.

[0301] As is obvious from the comparison of FIG. 19 and FIG. 21, in theembodiment according to the second invention, the number of steps couldbe reduced into ⅔ of that according to the related method, andresultantly the overall processing time could be reduced by 10% and thearea required for installing the apparatus could be reduced by 20%. Themanufacturing cost of the apparatus could also be reduced by 15%.

[0302] The etching unit with the defect inspection apparatusincorporated therein has been described as an exemplary unit in thesemiconductor manufacturing apparatus of the second invention, andwithout any trouble, other units in the semiconductor manufacturingapparatuses for carrying out the lithography, the film deposition (CVD,sputtering, plating), the oxidation, the impurities doping and so on mayalso be configured similarly so as to incorporate the defect inspectionapparatus.

[0303]FIG. 22 is a schematic diagram illustrating a defect inspectionapparatus of electron beam system equipped with a differentialexhausting mechanism, which is included in the semiconductormanufacturing apparatus according to the second embodiment of the secondinvention. In the drawing, only the main components including an opticalcolumn 51″ of electron beam defect inspection apparatus, a differentialexhausting section 52″, a guard ring 54″ and a moving stage 55″ areshown, but the other components including a control system, a powersystem, an exhausting system and so on are omitted. A wafer 53″ to betreated as the sample is fixed on the moving stage 55″ as surrounded bya guard ring 54″. The guard ring 54″ is made to have the same height(thickness) as that of the wafer 53″, allowing for a minute clearance57″ between the tip of the differential exhausting section 52″ and thewafer 53″ as well as the guard ring 54″ not to vary even during themoving operation of the stage. The area on the moving stage 55″ otherthan the area occupied by the guard ring 54″ and the wafer 53″ is alsomade flush with the wafer. Loading/unloading operation of the wafer iscarried out at a position where a center of a wafer exchange position56″ on the stage 55″ matches with a center of the inspection apparatus.According to the procedure in the method for unloading the wafer, thewafer is lifted up by three pins capable of moving up and down of themoving stage 55″, and a hand of a transfer robot is inserted under thewafer and lifted up to catch the wafer, and then the sample istransferred. Loading operation of the wafer can be carried out in theinverse sequence to that for unloading the wafer.

[0304]FIG. 23 is a schematic diagram illustrating the differentialexhausting section 52″ of FIG. 22. A differential exhausting body(52-3″) of the differential exhausting section 52″ is provided with anexhaust port I (52-1″) and an exhaust port II (52-2″), which arearranged concentrically, wherein the exhaust port I is exhausted by abroad band turbo-molecular pump and the exhaust port II is exhausted bya dry pump. Though not shown in the drawing, an exit of the electronbeam 202″ (an entrance for the secondary electrons) is configured to bea bore of φ1 mm×1 mm long, thereby accomplishing a small conductance.The minute clearance 57″ is maintained to be. typically 0.05 mm orsmaller (preferably 0.1 mm or smaller) by controlling the height of thestage 55″. As a result of the exhausting operation by coupling thedifferential exhausting section with a dry pump of an exhausting rate of1000 litter/min and a turbo-molecular pump of an exhausting rate of 1000litter/sec, a pressure of 10⁻³ Pa order and the pressure of 10⁻⁴ Paorder were obtained in the electron beam irradiation section and in thevicinity of the electron beam exit within the optical column,respectively.

[0305]FIG. 24 is a schematic diagram illustrating a third embodiment.This is an embodiment in which a image projection-type electron beaminspection apparatus is used as the electron beam defect inspectionapparatus. It is to be noted that the differential exhausting section isomitted in the drawing. A primary electron beam 202″ emitted from anelectron gun 201″ is shaped properly in a rectangular aperture andformed into an image of 0.5 mm×0.125 mm rectangle on a deflection centerplane of an E×B filter 205″ with the aid of a two-stage of lenses 203″and 204″. The E×B filter 205″, which is called also as the Wien filter,comprises an electrode 206″ and a magnet 207″ arranged to have astructure in which an electric field and a magnetic field are crossed ata right angle, and thus functions to deflect the primary electron beam202″ by an angle of 35° toward the direction of sample (the directionvertical to the sample), while allowing for the secondary electron beamfrom the sample to go through straight ahead. The primary electron beam202″ deflected by the E×B filter 205″ is contracted to be ⅖ in its sizeby lenses 208″ and 209″, and then projected onto the sample 210″. Thesecondary electrons 211″ emanated from the sample 210″, which containinformation of the pattern image, are after having been magnified by thelenses 209″ and 208″, advanced straight through the E×B filter 205″,magnified by lenses 212″ and 213″, intensified by 10,000 times by an MCP(Micro Channel Plate) and converted into a light by a scintillatorscreen 216″, and thus converted light passes through a relay opticalsystem 217″ and enters a TDI-CCD 218″ where the light is converted intoan electric signal synchronized with a scanning rate of the sample,which is in turn captured by an image display 219″ as a series ofimages. Further, the series of images are compared on time to aplurality cell images as well as a plurality of die images to therebydetect a defective portion on the surface of the sample (e.g., wafer).Further, a feature such as a shape, a position coordinate and a numberof the detected defects are recorded and output onto a CRT, for example.On one hand, for various kinds of sample substrate, the defect may bedetected in such a way that an appropriate condition is selected to eachdifferent sample substrate depending on a difference in a surfacestructure, such as an oxide film or a nitride film or a difference in apreceding step of processing, and then the electron beam is irradiatedin accordance with the selected condition, wherein after the irradiationprovided under the optimal irradiation condition, the image by theelectron beam is obtained so as to detect the defect.

[0306]FIG. 25 is a schematic diagram illustrating a configuration of afourth embodiment according to the second invention.

[0307] Four primary electron beams 302″ (302A″, 302B″, 302C″ and 302D″)emitted from an electron gun 301″ are shaped properly by an aperturestop 303″ and formed into respective images each having 10 μm×12 μmelliptical shape on a deflection center plane of an E×B filter 307″ by atwo-stage of lenses 304″ and 305″, wherein they are controlled by adeflector 306″ to make a raster scanning motion along the directionvertical to a sheet surface of the drawing so that they may beirradiated as a whole to cover a rectangular area of 1 mm×0.25 mmuniformly. Herein the four primary electron beams 302″ deflected by theE×B filter 307″ are formed into an crossover in an NA aperture 308″,contracted to ⅕ in its size by a lens 309″ and irradiated/projected ontoa sample (wafer) 310″ to cover an area of 200 μm×50 μm in the directionsubstantially vertical to the sample. Four secondary electron beams 312″emitted from a sample 310″, which contain information of a pattern image(sample image 311″), are magnified by lenses 309″, 313″ and 314″,applied with an angle compensation for the direction of serial movementof the sample and the direction of integration row of the TDI-CCD 319″by a magnetic lens 315″, and formed into a rectangular image (magnifiedprojection image 318″) resultant from the synthesized four secondaryelectron beams 312″ as a whole onto an MCP 316″. This magnifiedprojection image 318″ is intensified by the order of 10,000 times by theMCP 316″, converted into a light by a scintillator screen 317″, furtherconverted into an electric signal synchronized with a serially movingrate of the sample by a TDI-CCD 319″, captured as a series of images byan image display section (not shown) and then output onto a CRT, forexample, or stored in a memory device. From this image, a defect may bedetected through the cell comparison or the die comparison, and theposition coordinate, size or type thereof may be classified for furtherstoring, displaying and outputting operations.

[0308]FIG. 26 shows a method for irradiating the primary electron beamaccording to the present embodiment. The primary electron beam 302″consists of the four electron beams 302A″, 302B″, 302C″ and 302D″, eachbeam assuming a 10 μm×12 μm elliptical shape. Each one of those beamscan raster-scan a rectangular area of 200 μm×12.5 μm, thus collectivelycovers the rectangular irradiation area of 200 μm×50 μm withoutoverlapping one another. In the present embodiment, with the unevennessin irradiation in the order of +3% for the primary electron beams, andthe irradiation current of 250 μA per each electron beam, the totalirradiation current of 1.0 μA by the four electron beams could beobtained as a whole on the surface of the sample. By increasing thenumber of electron beams, the current can be increased more and therebya higher throughput will be obtained.

[0309] Though not shown in the drawing, the present apparatus furthercomprises in addition to the lenses, a limited field stop, a deflector(aligner) having four or more poles for aligning an trajectory of theelectron beam, an astigmatism compensator (stigmeter) and a plurality ofquadrupole lens (four-pole lens) for shaping the beam properly, and soon, which are units required for illumination and image formation of theelectron beam.

[0310] It is required that the electron beam irradiation sectionirradiates the sample surface with the electron beams in a rectangularor an elliptical shape as uniformly as possible with reduced unevennessof irradiation, and it is also requested to provide the electron beamirradiation to the irradiation area with a higher current in order toincrease the throughput. The related electron beam irradiation systemhas such high irradiation unevenness as ±10% and the electron beamirradiation current of about 500 nA in the irradiation area. Inaddition, the related system has been suffered from a problem that it issusceptible to a failure of image formation due to charge-up which iscaused by applying the electron beam irradiation all at once over alarge image observation area, as compared to the scanning-type electronbeam microscope (SEM) system, but the method according to the presentinvention in which a plurality of electron beams is used to scan andirradiate the sample could have reduced the irradiation unevenness tothe order of ⅓ of that of the related system. As for the totalirradiation current on the sample surface, two or more times as highcurrent value could be obtained by using the four electron beams. Byincreasing the number of electron beams, for example, up to the numberof 16, which may be reached easily, a further high current can beachieved thus to obtain a higher throughput. Further, since the rasterscanning operation by relatively narrow beams helps release the chargeson the sample surface, therefore the charge-up could be reduced down toat most {fraction (1/10)} as compared to the block irradiation.

[0311] The example of the electron beam defect inspection apparatus ofimage-projection system has been described as the embodiment, andwithout any trouble, the defect inspection apparatus of scanning-typeelectron microscope system (SEM system) may be used also.

[0312]FIG. 27 shows a defect inspection apparatus employing a imageprojection optical system according to a fifth embodiment of the secondinvention. This embodiment uses back-scattered electrons.

[0313] All of the components including the electron gun 601″ to theimage display section 619″ are the same as those in FIG. 24, andaccordingly those components designated by reference numerals 201″ to219″ in FIG. 24 are indicated by 601″ to 619″ respectively in FIG. 27.The embodiment of FIG. 27 is different from the embodiment of FIG. 24only in an orbit of the electron beams, wherein the orbit 620″ of thesecondary electron beams is, as shown in dotted line, emitted at a largeemission angle from the sample 610″ and accelerated in an acceleratingelectric field produced by the objective lens 609″, thereby convergedinto a small beam bundle to enter the objective lens 609″. On the otherhand, since the back-scattered electrons 621″ advance substantiallystraight ahead in the direction of the emission, an aperture diameter ofan aperture 622″ for limiting the beam has been made larger so as toobtain a signal having a sufficient S/N ratio. Since the back-scatteredelectrons have a relatively smaller energy width of the beam, ΔV, ascompared to the secondary electrons, therefore even with a somehowlarger diameter of the aperture 622″, yet the aberration can be reducedsatisfactorily.

[0314] An electron beam system according to an embodiment of a thirdinvention and a device manufacturing method using such a system will nowbe described.

[0315] The embodiment of the third invention relates to an electron beamsystem for providing an evaluation of a sample having a pattern withminimum line width equal to or less than 0.1 μm with high throughput andhigh reliability, and further to a device manufacturing method usingsuch a system.

[0316] Conventionally, in a defect inspection process of a variety ofmasks such as a stencil mask or a photo mask process, the inspection hasbeen carried out in such a manner that a primary electron beam isdirected to a sample, and secondary electrons emanated from the sampleare magnified as an image, which is in turn detected by a CCD detectoror a TDI detector so as to perform the inspecting operation (opticaltype inspection). Further, such en electron beam system has been known.The preceding patent applications are listed below:

[0317] Japanese Patent Laid-open Publication No. Hei 11-132975

[0318] Japanese Patent Laid-open Publication No. Hei 7-249393

[0319] Japanese Patent Application No. 2000-193104

[0320] Japanese Patent Application No. 2000-229101

[0321] In the electron beam system according to the related art, sincethe transmissivity of the secondary electron in the secondary opticalsystem is rather low, a large quantity of primary electron beam has tobe applied in order to obtain an image having necessary S/N ratio, whichcauses a problem that the sample surface is charged. Besides, there hasbeen another problem in conjunction with the effort to improve thetransmissivity that the beam is seriously unfocused and the contrast ofthe image is deteriorated.

[0322] The embodiment according to the third invention is directed toprovide an electron beam system that can solve the above problems.

[0323] First of all, an outline of the electron beam system according tothe embodiment of the third invention will be described.

[0324] [1] (FIG. 30: conjugate relationship: crossover produced by anelectron gun 12′—NA aperture 40′—principal plane of an objective lens32′)

[0325] The present embodiment is an electron beam system, in which aprimary electron beam emitted from an electron gun is directed to asurface of a sample prepared as an object to be inspected, and anelectron image formed by secondary electrons emanated from the sample ismagnified and detected, the system further comprising an NA aperturedisposed on a common path to both of the primary and secondary electronbeams and an electron lens in the vicinity of the sample surface,wherein a crossover produced by the electron gun and a principal planeof the electron lens and the NA aperture are in the conjugaterelationship to one another.

[0326] [2] Preferably, an NA aperture image may be formed on or in thevicinity of the principal plane of the electron lens by an electron lens38′ disposed in the electron lens side of the NA aperture.

[0327] [3] Further, a shaping aperture is arranged on the path of theprimary electron beam, wherein the shaping aperture and the samplesurface are conjugate surface, and the crossover of the electron gun bythe primary electron beam is formed in the NA aperture and on theobjective lens principal plane. Since this helps make the aberrationlow, allowing for a larger NA aperture with the same level of aberrationand thus a higher transmissivity of secondary electrons, therefore theimage having a satisfactory S/N ratio can be obtained even with a smallquantity of primary electron beam.

[0328] According to the present embodiment, the crossover image, the NAaperture and the objective lens principal plane are conjugate, and theshaping aperture and the sample surface are conjugate.

[0329] [4/5] (Beam hape and its intensity)

[0330] As described above, the present embodiment is configured suchthat the image of the NA aperture is formed in the vicinity of theprincipal plane of the electron lens disposed closely to the samplesurface. FIG. 30 shows its configuration. In FIG. 30, the electron lensis designated by reference numeral 32′, which is hereafter referred toas an objective lens 32′. With the configuration described above, thesecondary electrons emanated from the sample surface 34 a′ and passingthrough the NA aperture 40′ are exclusively guided into a secondaryoptical system and detected therein. FIG. 31 shows that illustratively.

[0331] The secondary electrons from the sample are emanated inaccordance with the cosine law as indicated by reference numeral 43′. Inspecific, the intensity of the secondary electrons emanated in thedirection at an arbitrary angle from the point of emanation “O” isproportional to the distance from the point of emanation O to anintersection point with a circumference indicated by reference numeral43′. Accordingly, a quantity of secondary electrons which can bereceived by the secondary optical system among those secondary electronsemanated from the center of the field of view of the sample isproportional to a volume surrounded by an inverse cone indicated byreference numeral 41′ and a spherical shape defined by the cosine law(one of the sections of which is indicated by the circumference 43′). Onone hand, the secondary electrons which can be received by the secondaryoptical system among those secondary electrons emanated from the rightend of the field of view are within a range of inverse cone indicated byreference numeral 42′.

[0332] The cone 41′ and the cone 42′ have the same apex angle α, but thevolume of the cone 41′ is larger than that of the cone 42′. The cone 41′includes a circular arc “AB”, while the cone 42″ includes a circular arc“CD”. From the comparison between those two cones (41′, 42′), thesecondary electrons emanated from the right end are less than thoseemanated from the center (on the optical axis 11′) of the sample 34′.Consequently, the secondary electron beam on the optical axis 11′ tendsto be brighter, while those off from the optical axis 11′ tends to bedarker.

[0333] In light of the above fact, the present embodiment provides anelectron beam system in which a primary electron beam is irradiated to asample surface, and secondary electrons emanated from the sample aremagnified and detected, wherein the beam configuration of the primaryelectron beam entering the sample surface is controlled to have such adistribution that its intensity is low in the vicinity of the opticalaxis and high in the location away from the optical axis. Similarly, inthe present embodiment, the electron beam system is characterized inthat the beam configuration of the primary electron beam entering thesample surface is controlled to have such a distribution that itsintensity is low in the vicinity of the optical axis and high in thelocation away from the optical axis. With this configuration, thedistribution of the secondary electrons that can be received by thesecondary optical system is no more dependent on the distance from theoptical axis but uniform, and so the detection signal intensity will bealso uniform without depending on the distance from the optical axis.

[0334] [6/7] (Position of E×B separator)

[0335] Further, the present embodiment provides an electron beam systemin which in order to reduce the distortion aberration of the image to bedetected, a primary electron beam is directed to a sample surfacevertically with the aid of an E×B separator, secondary electronsemanated from the sample surface are magnified by using at leasttwo-stage of electron lenses as an image to be detected, wherein the E×Bseparator is disposed between an electron lens in a location mostdownstream in the path of the secondary electron beam and a detector.Similarly, in the present embodiment, the electron beam system ischaracterized in that at least two-stage of electron lenses are disposedon the path of the secondary electrons, wherein the E×B separator isdisposed between the electron lens located in a downstream side of thetwo-stage of electron lenses and the detector.

[0336] [8/9] (Deflection by the magnetic field is two times as much asthat by the electric field)

[0337] The E×B separator has a function for deflecting the electron beampassing therethrough into an arbitrary direction. However, a degree ofthe deflection is subtly different in dependence on the energy of theelectron beam. Generally, the electron beam having lower energy tends tobe deflected to a great degree.

[0338] Herein, the present embodiment provides an electron beam system,in which a primary electron beam is directed to a sample surfacevertically with the aid of an E×B separator, and secondary electronsemanated from the sample surface are magnified as an image to bedetected, wherein the E×B separator defines an amount of deflectioncaused by the magnetic field to be about two times as much as that bythe electric field. Similarly, the electron beam system is characterizedin that the E×B separator defines the amount of deflection caused by themagnetic field to be about two times as much as that by the electricfield. With this configuration, even if the energy of the electron beampassing through the E×B separator varies, the electron beam may bedeflected in the same direction within a range of approximation.Resultantly, the detector can obtained the secondary electron beam ofbetter resolution.

[0339] [10] According to a specific configuration of the illustratedembodiment, the electron beam system is characterized in that the E×Bseparator has been set to deflect the secondary electrons with apotential as high as about 4000 ev and also to deflect the secondaryelectron beam at an angle of 7° to 15° relative to the optical axis ofthe secondary electron beam.

[0340] [11] (FIG. 34: Conjugate relationship, crossover produced by theelectron gun 212′—objective lens 232′NA aperture 240′)

[0341] Further, the present embodiment may be implemented as an electronbeam system applicable to an inspection of a mask. The presentembodiment provides an electron beam system, in which a primary electronbeam emitted from an electron gun is transmitted through a sampleprepared as an object to be inspected, and an electron image formed by atransmission electron beam having passed through the sample is magnifiedand detected, wherein an NA aperture is disposed on a path of thetransmission electron beam, an electron lens is disposed in the vicinityof the sample, and a crossover produced by the electron gun and.theelectron lens and the NA aperture are in conjugate relationships to oneanother with respect to the primary electron beam and the transmissionelectron beam.

[0342] [12] Preferably, the electron beam system is characterized inthat the crossover image of the electron gun by the transmissionelectron beam is formed on or in the vicinity of the principal plane ofthe electron lens.

[0343] [13] (Another conjugate relationship: shaping aperture216′—sample 234′)

[0344] Further, the electron beam system is characterized in that ashaping aperture is disposed on the path of the primary electron beam,and the shaping aperture and the sample are positioned in the conjugaterelationship with respect to the primary electron beam, wherein theimage of the shaping aperture by the primary optical system is formed onthe sample surface. With this configuration, since the electron beam isirradiated exclusively to the necessary and sufficient area, atemperature increase and a damage by the radiation in the sample can belimited to a minimal level. It makes possible to obtain the image havinga sufficient SIN ratio even with a small quantity of primary electronbeam.

[0345] [14/15](Magnified image formed before two-stage of lenses)

[0346] Further, there is provided an electron beam system in whichsecondary electrons emanated from a sample surface or an image ofelectrons having passed through the sample is magnified by at leasttwo-stage of electron lenses and detected, wherein a distortionaberration or a transverse chromatic aberration can be reduced byadjusting the position of the magnified image produced by the electronlens of the first stage so as to match with a certain position upstreamto the electron lens of the second stage. Similarly, the electron beamsystem is characterized in that at least two-stage of electron lensesare disposed on the path of the transmission electron beam, wherein theposition of the magnified image produced by the electron lens of thefirst stage is matched with a certain position upstream to the electronlens of the second stage. With this configuration, the distortionaberration of the detected image may be reduced.

[0347] [16/17] (Compensation parameter optimization)

[0348] There is provided an electron beam system in which a primaryelectron beam is irradiated to a sample and an image of secondaryelectrons emanated from the sample or an image of transmission electronhaving passed through the sample is magnified as an image to bedetected, or an electron beam system described above, the systemcharacterized in that a distortion aberration of the image is simulatedby calculation so as to determine a difference in distortion aberrationbetween absolute values of a third and a fifth order thereof, wherein acompensation parameter is optimized such that the difference may beminimized or the absolute value of the fifth order may be greater thanthat of the third order by 5-15%, and in response to the optimizedcompensation parameter, the position of the magnified image produced bythe electron lens of the first stage may be set.

[0349] [18/19] (Tuning of magnification, displacement of sampleposition)

[0350] Currently, two different types of stencil mask may be considered.One is a mask used in a projection system for reducing an image of themask to a quarter image on a wafer, while the other is a mask used in a1:1 projection lithography. The former does not require such a highresolution, but the mask area is as large as 25 mm×40 mm×16=16000 mm².In contrast, the latter has the mask area as small as 25 mm×40 mm=1000mm², but a high resolution is required.

[0351] In order to inspect two different types of stencil masksdescribed above, it is important to make variable a magnification of theimage of transmission electron having passed through the stencil mask.For changing the magnification without degrading the aberration, it hasbecome apparent from the simulation that preferably a distance between astencil mask 28′ and an objective lens 29′ serving as the magnifyinglens, or a working distance 31′, should be changed.

[0352] In this regard, the present embodiment provides an electron beamsystem in which electrons having passed through a sample are magnifiedas a transmission electron image by an electron lens disposed close tothe sample so as to be detected by either one of a CCD, a TDI or anEBCCD, wherein when the magnification for magnifying the transmissionelectron image is to be changed, a distance between the sample and theobjective lens is changed. Similarly, the electron beam system ischaracterized in that an adjusting means for changing a distance betweenthe electron lens disposed close to the sample and the sample isprovided to cope with a case where one sample is to be changed toanother sample having a different resolution. With this configuration,the magnification of the transmission electron image may be madevariable without deteriorating the aberration.

[0353] [20] (Magnetic lens, gap in the sample side)

[0354] For producing a magnified image of the secondary electrons or thetransmission electrons, once the transverse chromatic aberration hasbeen compensated for satisfactorily, an axial chromatic aberrationdetermines the ultimate aberration. Especially, in order to improve thetransmissivity of the secondary electron, it is important to reduce theaxial chromatic aberration. To this end, the electron beam system isfurther characterized in that the electron lens disposed in the vicinityof the sample surface includes an electro-magnetic lens having a gap ofa core located in the sample side. With this configuration, an axialmagnetic field distribution may form a maximum value in a locationdefined in the sample 65 side with respect to the gap location, whichreduces the axial chromatic aberration coefficient.

[0355] [21] (Semiconductor device manufacturing method: Checking ofwafer)

[0356] There is provided a manufacturing method of a semiconductordevice, in which the electron beam system described above is used toinspect for any defect of a semiconductor wafer or the sample to beinspected.

[0357] A specific example of this manufacturing method of asemiconductor device comprises respective steps as set forth below:

[0358] (1) A wafer manufacturing process for manufacturing a wafer (orwafer preparing process for preparing a wafer).

[0359] (2) A mask manufacturing process for fabricating a mask to beused in the exposure (or a mask preparing process for preparing mask).

[0360] (3) A chipping process for cutting out chips formed on the waferone by one to make them operative.

[0361] (4) An inspection process for inspecting a finished chip by usingthe electron beam system.

[0362] [22] (Semiconductor device manufacturing method: Checking of themask)

[0363] There is provided a manufacturing method of a semiconductordevice, in which a mask that has been inspected for any defect by usingelectron beam system described above is used.

[0364] A specific example of this manufacturing method of asemiconductor device comprises respective steps as set forth below:

[0365] (1) A process for fabricating a mask.

[0366] (2) A process for carrying out an inspection of the fabricatedmask by using the electron beam system.

[0367] (3) A process for manufacturing a variety of chips by using themask that has been inspected.

[0368] Further, the electron beam system is also applicable to alithography process in a wafer processing process. In that case, themask that has been inspected by using the electron beam system is usedto form a resist pattern in order to process selectively a thin filmlayer or a wafer substrate.

[0369] A preferred embodiment of a third invention will now be describedin detail with reference to the attached drawings. FIG. 29 shows anelectron beam system according to the third invention and an inspectionapparatus using the same electron beam system, wherein an electron beamsystem 10′ is shown in the left hand side and a control section 100′ isshown in the right hand side of the drawing. FIG. 30 shows a detailedconfiguration of the electron beam system 10′.

[0370] (Electron Beam System 10′)

[0371] An electron beam system 10′ comprises, as main componentsthereof, an electron gun 12′ for emitting an electron beam and othercomponents disposed in a downstream side of the electron gun 12′,including: a shaping aperture 16′ for shaping the electron beam into adesired rectangular shape; an E×B separator 20′ for separating asecondary electron beam from a primary electron beam; an electron lens(a magnifying lens 38′) having a function for magnifying the focusedelectron beam; a sample 34′ and a sample table 36′ carrying the sample34′; and an electron lens (objective lens 32′) disposed in the vicinityof a sample surface 34 a′ of the sample. Further, an NA aperture 40′ isdisposed on a primary path and also on a secondary path, and a detector70′ is disposed on the second path.

[0372] As thermal electron emission type electron gun 12′ is employed,which emits electrons by heating a cathode 12 a′. The electron cathode(emitter) serving as a cathode has employed lanthanum hexaboride (LaB₆).Any other materials may be used therefor as far as they have a highfusion point (i.e., a low vapor pressure at high temperature) as well asa small work function. In the present embodiment, the electron gun 12′comprises a single-crystal LaB₆ cathode 12 a′ having a tip of such asmall radius of curvature as 30 μmR, which is operative under aspace-charge-limited condition, thereby allowing the electron beamhaving a higher intensity and a lower shot noise to be emitted. Further,by setting a distance between the Wehnelt 12 b′ and an anode 12 c′ to beequal to or longer than 8 mm and additionally determining a condition ofthe electron gun current to achieve a high brightness, then thebrightness can reach to a value greater than Langmuir limit.

[0373] In this context, preferably the electron gun 12′ in the presentembodiment comprises the thermionic cathode 12 a′ and is operable underthe space-charge-limited condition. Alternatively, such an electron gunwith a small electron source image having an FE (Field Emitter), a TFE(Thermal Field Emitter) or a Schottky cathode may be used as theelectron gun 12′. It is to be noted that the “space-charge-limitedcondition” refers to such a condition that the cathode temperature isincreased higher than a certain temperature where an emission amount ofthe electron beam is less susceptible to the effect from the cathodetemperature.

[0374] A first electron lens, which is defined as a condenser lens 14′,is disposed in a direction of emission of the electron gun 12′ (a lowerright direction in the drawing). Further, the shaping aperture 16′ and asecond electron lens are disposed downstream on the path of the primaryelectron beam. This second electron lens is defined as an irradiationlens 18′. The primary electron beam emitted from the electron gun 12′ isconverged by the condenser lens 14′ to illuminate the shaping aperture16′. The primary electron beam is formed, by passing though the shapingaperture 16′, into a shaped beam having a desired shape, and isdeflected arbitrarily by a deflector (omitted in the drawing) to therebyirradiate an area in an inspected region on the sample 34′ at a certainmoment.

[0375] In this embodiment, it is also possible to employ an alternativeconfiguration in which two pieces of shaping apertures are disposedalong the optical path with the deflector interposed therebetween so asto make a shaped beam variable thus to adjust the irradiation area,wherein a system in which the shaping aperture 16′ is substituted with aplurality of apertures of different sizes to adjust the irradiation areamechanically can bring about a merit that can reduce an optical pass.

[0376] This embodiment is configured such that the primary electron beamis deflected by one or more deflectors so as to scan the entire samplein cooperation with the moving operation of the stage, andalternatively, a focal length of either one of the respective lenses(14′, 18′) may be changed to thereby form the crossover image having asmall diameter so as to scan the sample surface 34 a′. Furtheralternatively, a plurality of shaping apertures may be provided to formthe electron beam having a small diameter by reducing the overlappedarea of the apertures, and thus formed electron beam may be used for theregistration through its scanning operation.

[0377] Preferably, the irradiation area of the electron beam that passesthrough the shaping aperture 16′ and irradiates the sample 34′ may bespecified as a rectangular shape having long sides and short sides. Inthis case, the image formations in the long side directions of theirradiation area are carried out simultaneously, wherein by moving thesample table 36′ in the short side direction, a continuous movements ofthe irradiation area in the short side direction is performed. Since theinspection is carried out while moving the sample table 36′continuously, therefore the inspection can be achieved with a highthroughput even with a narrow width of the main field of view.

[0378] The E×B separator 20′ is disposed in a location downstream to theirradiation lens 18′. The electron beam that has been irradiateddiagonally relative to the sample surface 34′ is deflected by the E×Bseparator 20′ to be vertical to the sample surface 34 a′. The angle ofdeflection may be appropriately determined, which is within a range of5° to 30° in this embodiment.

[0379] In a location downstream to the E×B separator 20′, the NAaperture 40′ having a function for reducing an aberration of thesecondary optical system and a doublet lens (a paired electron lens) arearranged. In the doublet lens, for convenience, the one close to thesample 34 is defined as a first stage of lens, which is represented bythe objective lens 32′. The other one close to the E×B separator 20′ isdefined as a second stage of lens, which is represented by themagnifying lens 38′. Interposed between the E×B separator 20′ and thesample 34′ are the NA aperture 40′, the magnifying lens 38′, theobjective lens 32′ and the sample 34′, which are arranged in thissequence.

[0380] Once the electron beam is irradiated on the sample surface 34 a′,secondary electrons are emanated therefrom, and those secondaryelectrons pass through the doublet lens (32′, 38′) and the NA aperture40′. The aberration of the secondary electrons is reduced by the NAaperture 40′. After that, the secondary electron beam is deflected by apredetermined angle with the E×B separator 20′. In this embodiment, theangle of deflection is within a range of 5° to 20° (in the drawing, thesecondary electron beam is deflected by 100 toward the directionopposite to the electron gun 12′). The detector 70′ is arranged to bevertical relative to the direction of the deflected secondary electronbeam. The secondary electron beam is irradiated onto the detector 70′vertically.

[0381] (Detector 70′)

[0382] The detector 70′ may comprise an MCP (Multi Channel Plate) formultiplying the electrons without deteriorating the quality of image andan FOP (Fiber Optical Plate). The MCP and the FOP are arranged in thissequence along the direction of the irradiation of the electron beam.The detector 70′ further comprises a vacuum window, an optical lensserving as a relay optical system and a TDI detector serving as adetection sensor having a plurality of pixels.

[0383] It is to be noted that the configuration of this detector 70′ isnot limited to that specified above, but the detector 70′ may notcomprise the MCP or otherwise it may be configured to include a CCDusing elements sensitive to the electron beam (EBCCD).

[0384] (Control Section 100′)

[0385] The control section 100′ may be composed of a general-purposepersonal computer and the like as illustrated in FIG. 29. This computercomprises a control section main body 101′ for carrying out a variety ofcontrol and arithmetic operations according to a predetermined program,a CRT 103′ for displaying results of operations of the control sectionmain body 101′ and an input section 105′ such as a keyboard and/or amouse to allow an operator to input commands. It is a matter of coursethat the configuration may employ hardware dedicated for an inspectionapparatus or a workstation to be served as the control section 100′.

[0386] The control section main body 101′ may comprise a CPU, a RAM, aROM, a hard disk, a variety types of control substrates such as a videosubstrate and so on, though not shown. An electron image storage area107′ has been allocated on a memory such as the RAM or the hard disk forstoring electric signals received from the detector 70′, or digitalimage data of the image by the secondary electron beam emanated from thesample 34′. In addition, a reference image storage section 109′ forstoring previously a reference image containing no defect thereinresides on the hard disk. Further, in addition to the control programfor controlling the entire defect inspection apparatus, a defectinspection program 111′ has been stored on the hard disk for reading theelectron image data from the storage area 107′ and detectingautomatically the defect of the sample 34′ based on the image dataaccording to a predetermined algorithm. This defect inspection program111′ has a function of performing a matching operation of the referenceimage read out of the reference image storage section 109′ with anactually detected electron beam image so as to detect the defectiveportion automatically, and indicating an alarm to the operator in caseof determination that there is a defect existing. Further, it canperform the matching operation between electron images detected in theidentical locations of adjacent chips or between the detected images inthe identical cells at different locations within the same chip. At thattime, a display of the electron image 103 a′ may be indicated on thedisplay section of the CRT 103′.

[0387] (Feature of the Present Embodiment)

[0388] (1) Image Formation of an NA Aperture Image

[0389] In an electron beam system according to the present embodiment,the NA aperture 40′ is disposed on the path common to both of theprimary and secondary electron beams. Further, the objective lens 32′ isdisposed in the vicinity of the sample 34′. Herein, the crossoverproduced by the electron gun 12′, the principal plane of the objectivelens 32′ and the NA aperture are arranged so as to form the conjugaterelationships to each other with respect to the primary electron beam.With this arrangement, the electron source image produced by theelectron gun 12′ is formed into an image in the NA aperture 40′, and theimage of the NA aperture 40′ is further formed into an image on or inthe vicinity of the principal plane of the objective lens 32′. Owing tothis, the primary electron beam is converged around the optical axis onor in the vicinity of the principal plane of the objective lens 32′,thus making a beam flux smaller and thereby reducing the aberration.

[0390] Further, in this embodiment, the shaping aperture 16′ and thesample surface 34 a′ are designed to be conjugate planes. Besides, thecrossover image of the electron gun 12′ is formed in the NA aperture40′. This embodiment, due to the above-specified configuration,satisfies the condition that the electron source image is formed in theNA aperture 40′ and the aperture image of the shaping aperture 16′ isformed on the sample surface, and it also meets the Koehler illuminationcondition. With the above configuration, since the image of the NAaperture is formed on the objective lens, the beam flux in the objectivelens is made small, thereby achieving a low aberration.

[0391] Further, in this embodiment, the primary electron beam satisfiesthe Koehler illumination condition, and two-stage of electron lenses(the objective lens 32′, the magnifying lens 38′) is constructed. Withthis configuration, the primary optical system defining a short opticallength may be provided.

[0392] As described above, the present embodiment employs such a layoutthat the image by the NA aperture is formed on or in the vicinity of theprincipal plane of the objective lens 32′ serving as the electron lensdisposed close to the sample surface. With this configuration, sincethose secondary electrons directing toward the center of the objectivelens 32, including those emanated from the center and also from the edgeof the field of view, are exclusively received by the secondary electronsystem, the beam flux in the objective lens is made small, therebyachieving a low aberration.

[0393] A reason why the intensity distribution of the secondary electronis uneven will now be explained based on the cosine law illustrated inFIG. 31.

[0394] The secondary electrons from the sample are emanated inaccordance with the cosine law as indicated by reference numeral 43′. Inspecific, the intensity of the secondary electrons emanated in thedirection at an arbitrary angle from the point of emanation “O” isproportional to the distance from the point of emanation O to anintersection point with a circumference indicated by reference numeral43′. Accordingly, a quantity of secondary electrons which can bereceived by the secondary optical system among those secondary electronsemanated from the center of the field of view of the sample isproportional to a volume surrounded by an inverse cone indicated byreference numeral 41′ and a spherical shape defined by the cosine law(one of the sections of which is indicated by the circumference 43′). Onone hand, the secondary electrons which can be received by the secondaryoptical system among those secondary electrons emanated from the rightend of the field of view are within a range of inverse cone indicated byreference numeral 42′.

[0395] The cone 41′ and the cone 42′ have the same apex angle α, but thevolume of the cone 41′ is larger than that of the cone 42′. The cone 41′includes a circular arc “AB”, while the cone 42′ includes a circular arc“CD”. From the comparison between those two cones (41′, 42′), thesecondary electrons emanated from the right end are less than thoseemanated from the center (on the optical axis 11′) of the sample 34′.Consequently, the secondary electron beam on the optical axis 11′ tendsto be brighter, while those off from the optical axis 11′ tends to bedarker.

[0396] In the electron beam system according to this embodiment, thearrangement of the lenses is not telecentric (in a telecentric system,the primary electron beam is irradiated vertically relative to thesample surface both in the optical axis and in a location off from theoptical axis). With this arrangement, the primary electron beam is, onor in the vicinity of the optical axis, irradiated to the sample surfacein the vertical direction, but it tends to be irradiated more diagonallyas it is farther from the optical axis, resulting in a weak intensity ofthe primary electron beam in the edge region off from the optical axisand thus a weak intensity of the secondary electron beam to be emanated.In light of the above fact, the shaping aperture is configured to havethe shapes as illustrated in FIG. 32(a) and FIG. 32(b) so as to increasethe quantity of the primary electron beam passing through the edge ofthe shaping aperture, thereby increasing the intensity, as measured onthe sample surface, of the primary electron beam in the edge portion offfrom the optical axis, so that even if the primary electron beam isirradiated diagonally relative to the sample surface at an edge regionthereof, resultant intensity of the secondary electron beam to beemanated can be made as high as that from the optical axis portion asmeasured on the sample surface.

[0397] That is, the present embodiment provides an electron beam systemin which a primary electron beam is irradiated on the sample surface,and secondary electrons emanated from the sample is magnified as animage to be detected, wherein the beam shape of the primary electronbeam to be irradiated onto the sample surface is controlled to have sucha intensity distribution that is low around the optical axis and high inthe location away from the optical axis, so that the distribution of thesecondary electrons received by the secondary optical system may beindependent from the distance from the optical axis but uniform, andaccordingly the distribution of the detection signal intensity may beuniform without depending on the distance from the optical axis.

[0398] In this regard, a detailed explanation will be given below.

[0399] (2) Shaping Aperture Image

[0400] As described above, the NA aperture image is formed on or in thevicinity of the principal plane of the objective lens 32′. In this case,there arises a problem that the quantity of the emanated secondaryelectrons is high around the optical axis, which is getting lower in thelocation more distant from the optical axis. To solve this problem, theshaping aperture 16′ in the present embodiment is designed to have aconfiguration as shown in FIG. 32(a). This drawing shows the opening ofthe shaping aperture 16′ defined from the upstream side to thedownstream side with respect to the optical axis 11′. In this drawing,an inside region surrounded by a line of reference numeral 16 a′(opening shape) represents an opening 16 b′, through which the primaryelectron beam passes. The outside region of the line of referencenumeral 16 a′ defines an opening frame 16 c′, which blocks the primaryelectron beam.

[0401] As shown in the drawing, an opening width W1′ of the opening 16b′ defined around the center thereof (around the optical axis 11) isconstant. Starting from certain points away from the center region by apredetermined distance toward both edges, the opening width is graduallyexpanded wider finally to the width indicated as the opening width W2′defined in either edge. The width of the opening W2′ is determined to benarrower than that defined by a blur of the beam of the primary opticalsystem. The ratio of the opening width W1′ to the opening width W2′ isdetermined such that the secondary electron beam has its intensity ofthe same level both around the optical axis 11′ and in the otherregions. In the present embodiment, the opening width W2′ is 1.5 to 4times as wide as that of the opening width W1′.

[0402]FIG. 32(b) shows the irradiation intensity distribution of theprimary electron beams that have passed through the opening 16 n′ of theshaping aperture and reached the sample surface 34 a′. The primaryelectron beam having passed through the opening 16 b′ increases independence on the distance from the optical axis. As shown in FIG.32(b), the contour 17 a′ of the primary electron beam that has passedthrough the opening 16 b′ and formed into an image on the sample 34′ bythe lenses 38′and 32′ is approximately a rectangular shape.

[0403] Curves defined in the inner side of the contour 17 a′ are contourlines 17 b′ to 17 e′ indicating magnitudes of the primary electron beam.The quantity is getting greater as from the contour line 17 b′ towardthe contour line 17 e′. The reason why the quantity is getting greatertoward either edge is that since the shape of the opening 16 b′ isgetting wider toward either edge, and accordingly a larger quantity ofelectron beam passes through the opening 16 b′ in both edges (openingwidth W2′>opening width W1′).

[0404] The greatest irradiation intensity is observed in the sectiondefined by the line A-A in FIG. 32(b), and its intensity distribution isindicated by “A” in FIG. 33. FIG. 33 shows an irradiation intensitydistribution by taking the irradiation width on x-axis and theirradiation intensity on y-axis. The intensity distribution in thesection defined by the line B-B is indicated by “B” and that in thesection defined by the line C-C (central region) is indicated by “C”. Asshown in FIG. 33, the lateral widths of respective sections are all thesame. In contrast, from the point that they have different heights, itis seen that the electron beams that have the same width are stilldifferent from one another in their intensity depending on the distancefrom the optical axis 11. The irradiation intensity is greatest in theA-A section, and getting lower in the sequence of the B-B section andthen the C-C section. If the primary electron beam having such intensitydistribution is irradiated on the sample surface 34 a′, the secondaryelectrons to be received by the secondary optical system are notdependent on the distance from the optical axis 11′ but will beconstant. Further, the intensity of the secondary electrons can be madeuniform by adjusting the opening shape 16 a′ appropriately. Again, thepresent embodiment is not representative of the telecentricillumination, as stated above.

[0405] (3) (E×B Separator 20)

[0406] The function of the E×B separator will now be described. As shownin FIG. 30, the E×B separator 20′ consists of an electromagneticdeflector 22′ and an electrostatic deflector 24′. The electrostaticdeflector 24′ is located in the inner side of the electromagneticdeflector 22′. They are designed such that the ratio of deflectionproduced by the electrostatic deflector 24′ to that produced by theelectromagnetic deflector 22′ is 1:2. The optical axis direction of thesecondary electrons emanated from the sample surface 34′ is indicated asa reference line 60′. Since the electrostatic deflector 24′ and theelectromagnetic deflector 22′ are configured to provide the deflectionratio of 1:2, therefore when the secondary electrons pass through themagnifying lens 38′, which is a second stage of magnifying lens, andenter the E×B separator 20′, the secondary electrons are deflected bythe electromagnetic deflector 22′ toward the right by 20 degrees fromthe reference line 60′, while at the same time, it is deflected by theelectrostatic deflector 24′ toward the left by 10 degrees. As a result,the optical axis of the secondary electrons is deflected toward theright hand side by 10 degrees on balance relative to the reference line60′. The detector 70′ is arranged at a right angle with respect to theaxis 200′ that is tilted to the right by 10 degrees from the referenceline 60′. The detector 70′ is disposed so as to be spaced from the E×Bseparator 20′ by a predetermined distance. As described above, in thisembodiment, the secondary electrons are deflected by both of theelectric field and the magnetic field. As for its deflectionsensitivity, the deflection produced by the magnetic field is designedto be 20° toward the right, while the deflection produced by theelectric field to be 10° toward the left, that is, the deflection by themagnetic field is in the inverse direction to and two times as large asthat by the electric field.

[0407] In the E×B separator 20′ that has been set to deflect thesecondary electrons having the energy of 4502 eV by 20° toward the rightby the electromagnetic deflector 22′ and by 10° toward the left by theelectrostatic deflector 24′, the deflection angle of the secondaryelectrons of 4501 eV will be defined as follows.

[0408] At first, the secondary electrons are deflected by the deflectionangle (4502/4501)^(1/2)×20° toward the right by the electromagneticdeflector 22′. Secondly, the secondary electrons are deflected by thedeflection angle (4502/4501)×10° toward the left by the electrostaticdeflector 24′. Then, the difference is determined by the equation below:$\begin{matrix}{{{\left( \frac{4502}{4501} \right) \times 10} - {\sqrt{\frac{4501}{4501}} \times 20}} = {{10 \times \left( {1 + \frac{1}{4501}} \right)} - {20 \times \left( {1 + \frac{1}{4501}} \right)^{1/2}}}} & \left( {{Eq}.\quad 1} \right)\end{matrix}$

[0409] where, since the figures in the parentheses of the first and thesecond terms can be approximated by 1, therefore the result will be

≈10×(1)−20×(1)=−10 (deflected toward the right by 10°).

[0410] Thus, the difference in deflection between the electrostaticdeflector 24′ and the electromagnetic deflector 22′ is about −10°, whichshows that the electron beam of 4501 eV is also deflected to the rightby 10° similarly to the electron beam of 4502 eV. This means thataccording to this embodiment, even the secondary electrons havingdifferent energy can be deflected by the same angle by the E×B separator20′. This can help reduce the deflection chromatic aberration.Preferably, the deflection angle is in the order of 7° to 15°. Further,there is no need to limit the energy of the electron beam to bedeflected to 4500 eV, but the energy in the order of 4500 eV or in arange of 4000 eV to 5000 eV is feasible.

[0411] Further, the two-stage of lenses (the objective lens 32′ and themagnifying lens 38′) are disposed on the path of the secondaryelectrons, and the E×B separator 20′ is disposed in the locationdownstream to the magnifying lens 38′ arranged downstream most in thesecondary electron beam path, that is, between the magnifying lens 38′and the detector 70′. Furthermore, in the present embodiment, thelocation of the E×B separator 20′ is defined in the detector 70′ sidewith respect to the magnifying lens 38′.

[0412] Owing to this arrangement, even if the deflection amount ratio ofthe electrostatic deflector 24′ to the electromagnetic deflector 22′ isslightly out of the ratio of 1:2, a difference in deflection chromaticaberration may, if any, fall in a range of submicron order on thedetector 70′ because of the short distance between the E×B separator 20′and the detector 70′. Further, since the pixel size is magnified on thedetector 70′ (in one example, assuming 640 times for the 50 nm pixel,resulting in the 32 μm pixel size), the quantity of difference inaberration would not cause any problem at all in the inspectionprecision of the semiconductor device. Especially in this embodiment,the arrangement of the E×B separator 20′ defined in the detector 70′side with respect to the magnifying lens 38′ may reduce the degree ofaberration to be further low.

[0413] As for the configuration of the E×B separator 20′ for deflectingthe secondary electron beam, the number of windings of the coil of theelectromagnetic deflector 22′ may be increased or decreased and/or thevoltage or current to be applied thereto may be increased or decreased.Alternatively, a space between the electrodes of the electrostaticdeflector, or the gap, may be adjusted in order to deflect the secondaryelectrons by a predetermined degree of angle. Further alternatively, thesecondary electron beam is not limited to the secondary electrons butmay be back-scattering electrons.

[0414] (Embodiment 2)

[0415]FIG. 34 shows an electron beam system according to a secondembodiment of the third invention. FIG. 34 represents an electron beamsystem that employs a stencil mask as the sample and carries out aninspection of the stencil mask. In this embodiment, an electron beam (aprimary electron beam) emitted from an electron gun 212′ having a LaB₆cathode is irradiated onto a condenser lens 214′ and a shaping aperture216′ having a rectangular opening, and the electron beam having passedthrough the shaping aperture 216′ is transmitted through an irradiationlens 218′ so as to be irradiated to a stencil mask 234′ prepared as thesample.

[0416] In the downstream side to the stencil mask, a first electron lens(an objective lens 232′) and in the location further downstream, asecond electron lens (a magnifying lens 238′) are disposed as themagnifying lenses. The electron beam transmitted through the stencilmask 234′ (the transmission electron beam) is magnified in two stages bythe objective lens 232′ and the magnifying lens 238′ to form a magnifiedimage on a detector 270′. An NA aperture 240′ is disposed on a path ofthe transmission electron beam in the downstream side to the two-stageof lenses. The NA aperture 240′ is disposed in the vicinity of themagnifying lens 238′ in the detector side thereof. The detector 70′ isdisposed downstream to the NA aperture 240′. In this embodiment, thedetector 270′ employs an EBCCD using the element sensitive to theelectron beam. The image detected by the detector is sent to a controlsection 100′, as is the case of the electron beam system 10′ shown inFIG. 29, where a specified analysis and inspection process is appliedthereto.

[0417] In this embodiment, a crossover produced by the electron gun212′, the objective lens 232′ and the NA aperture 240′ are in theconjugate relation to each other. Further, the shaping aperture 216′ isarranged on the path of the primary electron beam so as to establish theconjugate relationship between this shaping aperture 216′ and the sample234′ (the sample surface). With this arrangement, the image produced bythe shaping aperture 216′ is formed on the sample 234′ (the samplesurface). Further, the crossover image produced by the electron gun 212′is formed on or in the vicinity of the principal plane of the objectivelens 232′.

[0418] According to the configuration described above, since theelectron beam contributing the aperture image is allowed to pass closeto the optical axis 205′ in the proximity to the objective lens 232′,therefore the aberration can be reduced low in the image to be detected.Further, the Koehler illumination condition can be satisfied.

[0419] (Position of the Magnified Image)

[0420] It has been made apparent from the simulation that the distortionaberration of image detected when the image (magnified image) of thestencil mask 234′ by the objective lens 232′ serving as the first stageof electron lens is formed on the certain point 231′ defined in nearside or upstream to the second stage of magnifying lens (correspondingto the second stage of electron lens) 238′ can be minimal. In thisregard, the point on which this magnified image is established will nowbe described. It is to be noted that as the compensation parameter inthis simulation, the evaluation is made on, in addition to a distance“L” between the magnified image 231′ and the magnifying lens 238′, athird order of distortion proportional to the third power of a distancefrom the optical axis 205′ and a fifth order of distortion proportionalto the fifth power of the distance from the optical axis 205′.

[0421]FIG. 35 shows the distortion as a function of the distance Lbetween the point on which the magnified imager 231′ is formed and themagnifying lens 238′. In FIG. 35, the horizontal axis indicates thedistance L, and the vertical axis indicates a magnitude of thedistortion determined from the calculation. Herein, the left curve isthe third order of distortion S3 and the right curve is the fifth orderof distortion S5. It is to be noted that since the third order ofdistortion S3 is represented by positive values, while the fifth orderof distortion S5 is represented by negative values, therefore FIG. 35indicates absolute values for both values.

[0422] As shown in FIG. 35, it has been determined from the result ofthe simulation that the distances L where one of the distortions (S3,S5) becomes 0 does not coincide with that of the other. The distortion 0for S3 is observed on the distance L3, while the distortion 0 for S5 ison the distance L5. That is, the distortions for S3 and S5 would notfall on 0 at the same time. Based on this finding, the presentembodiment employs such a distance L that makes the absolute values forboth distortions substantially equal as an appropriate distance L1. Thisdistance L1 defines the value where the absolute values of the thirdorder and the fifth order of distortion aberrations are minimal.

[0423]FIG. 36 shows the third order of distortion S3 and the fifth orderof distortion S5 for the distance of L1. In FIG. 36, the horizontal axisrepresents a distance from the optical axis 205, while the vertical axisrepresents the magnitude of distortion. Since the distortion appearssymmetrical in the lateral direction with respect to the optical axis205, FIG. 36 shows the distortion exclusively in the right hand side. Inthe drawing, the rising curve represents the third order of distortionS31 and the dropping curve represent the fifth order of distortion S51.The difference between them is represented by reference numeral S71. Asshown in FIG. 36, the distortion has been successfully reduced by 20% byoptimizing the compensation parameter. This can help further reduce thedistortion aberration of the image to be detected as well as thetransverse chromatic aberration.

[0424] Further, in the present embodiment, the distance L may be set notonly to the distance where the absolute value of the third order and thefifth order of distortion aberrations is minimized but also to thedistance where the absolute value of the fifth order distortion(distortion aberration) is greater than the absolute value of the thirdorder of distortion (distortion aberration) by 5% to 15%. The distance Lwhere the fifth order of distortion S5 is greater than the third orderof distortion S3 by 10% is indicated as L2 (see FIG. 35). The thirdorder of distortion and the fifth order of distortion are determinedrespectively when the distance is set to L2, and the differencetherebetween is indicated as reference numeral S72 in FIG. 36. Thedifference of distortion S72 is shown to be reduced further than thedifference of distortion S71 by 13%.

[0425] The configuration of the simulation for setting the point of themagnified image to be produced by the first stage of electron lens (theobjective lens 232′, or the objective lens 32′ in the embodiment 1) inresponse to that compensation parameter will now be described withreference to FIG. 29 used in conjunction with the embodiment 1. Theprogram 113 for calculating the values for the third order and the fifthorder of distortion aberrations through the simulation and determiningthose absolute values is installed. In addition, such a program 115′ isinstalled that may set the point of the magnified image to be producedby the first stage of electron lens (magnifying lens) such that anabsolute value of the sum of those values calculated by the program 113′is minimum or that the absolute value of the fifth order of distortionis greater than that of the third order of distortion by about 5 to 15%.The point of the magnified image is set by adjusting the intensity ofthe electric field in the objective lens 232′.

[0426] (Displacement of Z-Position of the Sample)

[0427] Currently, two different types of stencil mask may be considered.One is a mask used in a projection system for reducing an image of themask to a quarter image on a wafer, while the other is a mask used in a1:1 projection lithography (LEEPL). The former does not require such ahigh resolution, but the mask area is as large as 25 mm×40 mm×16=16000mm² requiring high throughput. In contrast, the latter has the mask areaas small as 25 mm×40 mm=1000 mm², but a high resolution is required.

[0428] In order to inspect two different types of stencil masksdescribed above, it is important to make variable a magnification of theimage of transmission electron having passed through the stencil mask.For changing the magnification without degrading the aberration, it hasbecome apparent from the simulation that preferably a distance betweenthe stencil mask 28′ and the objective lens 29′ serving as themagnifying lens, or a working distance 31′, should be changed.

[0429] Based on this finding, in the present embodiment, when themagnification for magnifying the transmission electron image is to bechanged, a distance between the stencil mask 234′ as the sample and theobjective lens 232′ is changed. With this configuration, themagnification of the transmission electron image can be made variablewithout deteriorating the aberration.

[0430] To make variable the magnification of the image of transmissionelectron having passed through the stencil mask 234′, this embodimentallows the position of the stencil mask 234′ to be moved in thedirection of the optical axis 205′. In FIG. 34, the position of thestencil mask 234′ after movement is indicated by reference numeral 234a′. The magnification of 640 on the position indicated by referencenumeral 234′ can be reduced to the magnification of 320 by moving themask to the position indicated by reference numeral 234 a′, or moving itaway from the objective lens 232′. Thus, this embodiment makes thedistance between the sample 234′ and the objective lens 232′ variable.

[0431] As for the primary electron beam in this case, assuming that theimage forming condition of the crossover by the NA aperture 240′ is keptunchanged, the image forming condition of the mask image by the shapingaperture 216′ should allow a certain level of blur of the image. To thisend, in a preferred embodiment, the shaping aperture 216′ is providedwith a plurality of differently shaped apertures. In FIG. 34, they areindicated by reference numerals 216 a′ to c′. When the magnification ofthe transmission image is to be changed, preferably the size of theshaping aperture 216′ may be changed by switching it to either one ofthose designated by reference numerals 216 a′ to c′ to thereby changethe illumination area.

[0432] As for the means for moving the stencil mask 234′, in otherwords, the means for adjusting the distance between the sample (stencilmask 234′) and the electron lens (objective lens 232′) located close tothe sample, it may be implemented in a form in which some actuator isinterlocked with the stencil mask 234′ so as to move it. Alternatively,it may be implemented in another form in which a cassette for carryingthe stencil masks 234′ and a holder section for receiving the cassetteare provided, wherein the position for carrying the stencil masks 234′is changed for each cassette, and when the sample is exchanged toanother, the entire cassette including the sample is replaced, therebychanging the distance between the sample and the objective lens.

[0433] (Structure of the Objective Lens 301′)

[0434] For producing a magnified image of the secondary electrons or thetransmission electrons, once the transverse chromatic aberration hasbeen compensated for satisfactorily, an axial chromatic aberrationdetermines the ultimate aberration. Especially, in order to improve thetransmissivity of the secondary electron or the like, it is important toreduce the axial chromatic aberration. FIG. 37 shows a structure of anobjective lens 300′ aiming for reducing the axial chromatic aberrationwith a large angle of numerical aperture. This objective lens 300′ canbe used as the objective lens 32′ shown in FIG. 29 or the objective lens29′ shown in FIG. 34. FIG. 37 is a longitudinal sectional view of theobjective lens 300′ along the optical axis 299′. In FIG. 37, referencenumeral 299′ designates the optical axis. The electromagnetic lensserving as the objective lens 300′ has an annular structure with a pathformed in the center thereof for allowing the electron beam to passthrough. The electromagnetic lens 300′ includes an annular lens gap 305′formed in the sample side thereof, which is oriented toward the sample303′ side. In this embodiment, the lens gap 305′ is defined in theposition to be symmetrical around the optical axis 299′. The width ofthe lens gap 305′ may be set appropriately in dependence on the designof the electromagnetic lens 300′.

[0435] The axial magnetic field distribution for the case provided withthe lens gap 305′ is indicated by B1 in the drawing. The axial fielddistribution for the case provided with the lens gap 307′ in the opticalaxis 299′side according to the related art structure is indicated by B2.Defining as P1 the Z position having a maximum value in the axialmagnetic field distribution B1 and as P2 the Z position having a maximumvalue in the axial magnetic field distribution B2, then the position P1is much closer to the sample 303′ than the position P2. Thus, providingthe lens gap 305′ in the sample 303′ side forms the Z positionrepresenting the maximum value near to the sample. Owing to this, theaxial chromatic aberration coefficient can be reduced.

[0436] Further, preferably two pieces of electrodes dedicated for theelectrostatic lens may be arranged between the electromagnetic lens 300′and the sample 303′. In this embodiment, the electrodes 309′ and 311′serving as the electrostatic lens are disposed between theelectromagnetic lens 300′ and the sample 303′. Herein, a positive highvoltage is applied to the electrode 309′, and the electrode 311′ and theelectromagnetic lens magnetic pole 301′ are grounded, thereby allowingthis unit of components to be functional as an uni-potential lens.Besides, applying a negative high voltage to the sample 303′ allows theunit to be functional as a decelerating-electric field lens, therebyfurther reducing the axial chromatic aberration.

[0437] The aberration can also be reduced by aligning the peak of theaxial magnetic field distribution with the position of the electrode309′ of the two pieces of electrostatic lenses (309′, 311′) by changingthe distance L between the lens gap 305′ of the electrostatic lens 300′and the optical axis 299′. In the drawing, the above-described positionis indicated by reference numeral P3. It is to be noted that theelectrode 309′ is the electrode disposed in the electromagnetic lens300′ side. In this case, only the single electrode 309′ may be provided.

[0438] In the case where the electron beam system according to theembodiment of the third invention is applied to a device manufacturingmethod, the method may consist of the process similar to those shown inFIG. 16 and FIG. 17A, for example.

[0439] 1. In the embodiment according to the third invention, since theaperture or the aperture image is provided in the vicinity of theprincipal plane of the objective lens, the electron beam contributing tothe pattern image passes through the area near to the optical axis inthe region around the objective lens, so that the aberration can bereduced. Further, the intensity of the secondary electrons can be madeuniform by adjusting the geometry of the shaping aperture.

[0440] 2. Further, since the E×B separator is disposed between the lastelectron lens and the detector, therefore the aberration can besuppressed to a lower degree as compared with the pixel size even withsome level of deflection aberration existing.

[0441] 3. Further, since by making the magnitude of electromagneticdeflection double of that of the electrostatic deflection, even theelectron beams having different energy can be deflected by about thesame degree, the deflection chromatic aberration can be reduced.

[0442] 4. Further, in the second embodiment, since the two-stage oflenses can reduce the magnification chromatic aberration and make asmall value of distortion, therefore the inspection can be provided forthe stencil mask with high precision. Further, the magnification can bechanged without deteriorating the aberration level by changing theposition of the stencil mask or the sample on the optical axis.

[0443] 5. Further, the lens structure with a small axial chromaticaberration may be provided by arranging the lens gap in the sample side.Further, the axial chromatic aberration can be reduced more by combiningthe electromagnetic lens with the electrostatic lens.

[0444] 6. Yet further, since the primary electron beam satisfies theKoehler illumination condition and the two-stage of electron lenses areincluded in the configuration, the primary optical system defining ashort optical length can be provided.

[0445] Although only some exemplary embodiments of this invention havebeen described in detail above, those skilled in the art will readilyappreciated that many modifications are possible in the exemplaryembodiments without materially departing from the novel teaching andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

[0446] The entire disclosure of Japanese Patent Application No.2002-253197 filed on Aug. 30, 2002, No. 2002-319687 filed on Nov. 1,2002 and No. 2003-000178 filed on Jan. 6, 2003 each includingspecification, claims, drawings and summary is incorporated herein byreference in its entirely.

What is claimed is:
 1. An electron beam system comprising: an electrongun for emitting an electron beam and for irradiating said electron beamagainst a sample; an electron lens for magnifying the electron beamhaving passed through the sample; and a detector for detecting saidmagnified electron beam so as to form an image of the sample.
 2. Anelectron beam system in accordance with claim 1, in which said sample isa stencil mask or a mask having a pattern formed on a membrane.
 3. Anelectron beam system in accordance with claim 1 or 2, further comprisingan NA aperture disposed between the electron gun and said sample,wherein said electron beam is passed through the NA aperture, therebyallowing the well-collimated electron beam to be irradiated to saidsample.
 4. An electron beam system in accordance with any one of claims1 through 3, further comprising at least one shaping aperture disposedbetween the electron gun and said sample, wherein said electron beam ispassed through said shaping aperture and irradiated to said samplesurface, thereby allowing an image of said shaping aperture to be formedon the surface of said sample.
 5. An electron beam system in accordancewith any one of claims 1 through 3, further comprising a plurality ofshaping apertures disposed in the vicinity of an optical axis of saidelectron beam system, wherein an area on said sample to be irradiated ismade variable by changing overlaps of said plurality of shapingapertures with each other.
 6. An electron beam system in accordance withany one of claims 1 through 5, in which said electron gun has athermionic emission cathode and is operable under thespace-charge-limited condition.
 7. An electron beam system in accordancewith claim 1, further comprising at least two-stage of electron lensesdisposed between said sample and said detector, wherein said electronbeam passes through said sample and further through said two-stage ofelectron lenses to be irradiated onto said detector.
 8. An electron beamsystem in accordance with claim 1, further comprising an entrance pupilof an irradiation lens system disposed between said electron gun andsaid sample, wherein a source image is formed in said entrance pupil. 9.An electron beam system in accordance with claim 8, further comprising amagnifying lens disposed between said sample and said detector, whereina magnification of said magnifying lens is made variable in response toa size of an irradiation area of said electron beam as measured on thesample.
 10. An electron beam system in accordance with claim 5, in whichthe irradiation area of said electron beam on said sample is defined tobe a rectangular shape having long sides and short sides by changing theoverlaps of said plurality of shaping apertures with each other; andsaid system further comprises a sample table on which said sample isloaded; wherein a detection of said sample is carried out by saiddetector while moving said sample table carrying the sample continuouslyin the direction of said short sides.
 11. An electron beam system inaccordance with claim 1, further comprising a scanning means forcontrolling said electron beam to make a scanning motion in astep-by-step manner or continuously.
 12. An electron beam system inaccordance with claim 1, in which said detector comprises: ascintillator that changes the electron beam to an image of light; anoptical lens for adjusting a size of the image of light produced by saidscintillator or an optical system for projecting said image of light ata ratio of 1 to 1; and either one of a CCD detector or a TDI detector onwhich the image of light whose size has been adjusted by said opticallens is to be formed.
 13. An electron beam system in accordance withclaim 1, in which said electron gun is such a electron gun of smalllight source image having a FE, a TFE or a Schottky cathode.
 14. Anelectron beam system in accordance with claim 1, in which said electrongun is disposed under said sample, and said detector for detecting adefect in said sample is disposed above said sample.
 15. An electronbeam system in accordance with claim 1, in which a plurality ofmagnifying lenses for magnifying the electron beam is disposed betweensaid electron gun and said detector, wherein a magnifying lens servingas the first one to magnify the electron beam that has passed throughsaid sample is a doublet lens.
 16. An electron beam system in accordancewith claim 15, in which an NA aperture is disposed between saidplurality of magnifying lenses, wherein said NA aperture is able toremove those electron beams of bad collimation that have been scatteredby said sample.
 17. An electron beam system in accordance with claim 12,in which said scintillator is disposed in vacuum; said optical lens andsaid CCD or TDI detector are disposed in atmosphere; and a vacuum windowis arranged between said scintillator and said optical lens for takingout said image of light so as to be directed to said optical lensdisposed in atmosphere.
 18. An electron beam system in accordance withclaim 12, in which said scintillator, said optical lens and said CCD orTDI detector are disposed in vacuum.
 19. An electron beam system inaccordance with claim 1, in which said detector comprises an imagedetector, wherein said image detector is composed of an MCP and anEB-CCD detector or an EB-CCD, or otherwise a MCP and an EB-TDI detectoror an EB-TDI.
 20. An electron beam system in accordance with claim 1, inwhich a second detector for detecting secondary electrons or backscattering electrons, which are generated upon scanning of said samplewith said electron beam, is disposed between said sample and saidelectron gun.
 21. An electron beam system in accordance with claim 20,in which by changing a focal length of the lens, a crossover image isformed so as to scan a sample surface of said sample with said crossoverimage, or by reducing an overlap between two shaping apertures, anelectron beam of small diameter is produced so as to scan the samplesurface of said sample with said electron beam of small diameter,thereby carrying out a registration of said sample.
 22. An electron beamsystem in accordance with claim 1, in which an equivalent frequency ofsaid system is set to be equal to or higher than 200 MHz.
 23. Anelectron beam system in accordance with any one of claims 1 through 22,further comprising: a storage unit in which reference pattern data isstored in advance; and a control unit for comparing image data obtainedfrom the electron beam having passed through said sample to said patterndata, wherein said control unit carries out the defect inspection ofsaid sample based on the comparison of said image data to said patterndata.
 24. An electron beam system, in which an electron beam emittedfrom an electron gun is irradiated to a stencil mask, and electronshaving passed through said stencil mask are detected to thereby detect adefect in said stencil mask.
 25. An electron beam system in accordancewith claim 24, in which said electron beam irradiation section comprisesa plurality of optical systems.
 26. A manufacturing method of asemiconductor device comprising a step of using a stencil mask which hasbeen inspected for any defect by using the electron beam system definedby any one of claims 22 through
 25. 27. A semiconductor manufacturingapparatus for a wafer or a mask, said apparatus including a defectinspection apparatus incorporated therein.
 28. A semiconductormanufacturing apparatus in accordance with claim 27, in which saiddefect inspection apparatus is such a defect inspection apparatus thatuses an energy beam, wherein said defect inspection apparatus isintegrated with said semiconductor manufacturing apparatus to constructa single unit.
 29. A semiconductor manufacturing apparatus in accordancewith claim 27 or 28, in which said semiconductor manufacturing apparatuscomprises an etching (pattern forming) section, a cleaning section, adrying section, an inspecting section equipped with said defectinspection apparatus, and a load section and an unload section, whereinsaid inspecting section is arranged close to either one or two or threeof said etching section, said drying section and said unload section.30. A semiconductor manufacturing apparatus in accordance with any oneof claims 27 through 29, in which said defect inspection apparatus is anelectron beam defect inspection apparatus, wherein said semiconductormanufacturing apparatus includes a cleaning unit and a drying unit eachincorporated therein.
 31. A semiconductor manufacturing apparatus inaccordance with claim 30, in which said electron beam defect inspectionapparatus is equipped with a differential exhaust system.
 32. Asemiconductor manufacturing apparatus in accordance with claim 31, inwhich an electron beam irradiation area on a sample surface is evacuatedby said differential exhausting system.
 33. A semiconductormanufacturing apparatus in accordance with any one of claims 30 through32, in which said defect inspection apparatus is an electron beam defectinspection apparatus of scanning-type electron microscope (SEM) system.34. A semiconductor manufacturing apparatus in accordance with claim 33,in which a primary electron beam used in said electron beam defectinspection apparatus is composed of a plurality of electron beams, andsecondary electrons from the sample is deflected from an optical axis ofthe primary electron beam by an E×B separator (Wien filter) so as to bedetected by a plurality of electron beam detectors.
 35. A semiconductormanufacturing apparatus in accordance with any one of claims 30 through32, in which said defect inspection apparatus is an electron beam defectinspection apparatus of image projection-type electron microscopesystem.
 36. A semiconductor manufacturing apparatus in accordance withclaim 35, in which a primary electron beam used in said electron beamdefect inspection apparatus is composed of a plurality of electronbeams, wherein said plurality of electron beams is irradiated to asample while scanning it, and secondary electrons from the sample isdeflected from an optical axis of the primary electron beam by an E×Bseparator (Wien filter) so as to be detected by a two-dimensional orline image sensor.
 37. An electron beam system representing a defectinspection apparatus, in which an electron beam emitted from a LaB₆electron gun is shaped properly and irradiated to a sample, and anelectron beam emanated from said sample is formed into an image by anoptical system of image projection-type electron microscope system,wherein said electron beam system comprises a load lock chamber forloading and unloading, and said LaB₆ electron gun is operable under aspace-charge-limited condition.
 38. An electron beam system inaccordance with claim 37, in which said electron beam emanated from saidsample consists of back-scattered electrons or transmission electrons.39. An electron beam system in accordance with claim 37, which hasemployed such a system, in which a image projected sample image isconverted into an optical image by a scintillator screen, and saidoptical image is formed on a TDI detector by an FOP or a lens system.40. An electron beam system in accordance with claim 37, which hasemployed such a system, in which a image projected sample image isformed on a TDI detector having a sensitivity to the electron beam. 41.An electron beam system in accordance with claim 37, in which saidsample is fixedly mounted on a sample table by an electrostatic chuck, alaser interferometer is arranged for measuring a position of said sampletable, and said sample is fixedly held by the electrostatic chuck evenin said load lock chamber.
 42. A semiconductor device manufacturingmethod, in which a wafer in the course of processing is inspected byusing the defect inspection apparatus defined by any one of claims 27through
 41. 43. A device manufacturing method, in which a defectinspection and a defect analysis are applied to a wafer or a mask afterone of processing processes is finished, and a result therefrom is fedback to the processing process.
 44. An electron beam system, in which aprimary electron beam emitted from an electron gun is irradiated to asample surface of a sample prepared as a subject to be inspected, and anelectron image formed by a secondary electron beam emanated from saidsample is magnified and detected, said system comprising, an NA aperturedisposed on an optical path common to said primary electron beam andsaid secondary electron beam, and an electron lens disposed in thevicinity of said sample surface, wherein a crossover produced by saidelectron gun, said electron lens and said NA aperture are in theconjugate relationships to each other.
 45. An electron beam system inaccordance with claim 44, in which said NA aperture image is formed onor in the vicinity of a principal plane of said electron lens.
 46. Anelectron beam system in accordance with claim 45, in which a shapingaperture is arranged on said path of said primary electron beam, andsaid shaping aperture and said sample are defined as conjugate planes.47. An electron beam system, in which a primary electron beam isirradiated to a sample surface, and secondary electrons emanated fromthe sample is magnified as an image to be detected, in which aconfiguration of beam to be irradiated to the sample surface is designedto have a distribution of its intensity that is lower in the vicinity ofan optical axis and higher in a location away from the optical axis. 48.An electron beam system in accordance with any one of claims 44 through46, in which a configuration of beam to be irradiated to the samplesurface is designed to have a distribution of its intensity that islower in the vicinity of an optical axis and higher in a location awayfrom the optical axis.
 49. An electron beam system, in which a primaryelectron beam is directed into a sample surface vertically by using anE×B separator, and secondary electrons or back scattering electronsemanated from said sample surface are magnified as an image by using atleast two-stage of lenses to be detected, wherein said E×B separator isdisposed between an electron lens located downstream most in a path ofsaid electron beam and a detector.
 50. An electron beam system inaccordance with any one of claims 44 through 48, in which at leasttwo-stage of lenses are disposed on a path of secondary electrons orback scattering electrons, wherein said E×B separator is disposedbetween one of said two-stage of electron lenses that is locateddownstream in said path of said electron beam and a detector.
 51. Anelectron beam system, in which a primary electron beam is directed intoa sample surface vertically by using an E×B separator, and secondaryelectrons or back scattering electrons which are emanated from saidsample are magnified as an image to be detected, wherein said E×Bseparator is configured such that a deflection angle of the secondaryelectrons caused by a magnetic field is about two times as large as thatby the electric field.
 52. An electron beam system in accordance withclaim 49 or claim 50, in which said E×B separator is configured suchthat a deflection angle of the secondary electrons caused by a magneticfield is about two times as large as that by the electric field.
 53. Anelectron beam system in accordance with claim 51 or 52, in which saidE×B separator is set to deflect the secondary electrons or the backscattering electrons having a level of about 4500 eV, and also set todeflect the secondary electron beam by an angle of 70 to 150 relative toan optical axis of the secondary electron beam.
 54. An electron beamsystem, in which a primary electron beam emitted from an electron gun isirradiated to a sample prepared as a subject to be inspected, and anelectron image formed by its transmission electron beam having passedthrough the sample is magnified and detected, wherein an NA aperture isdisposed on a path of said transmission electron beam and an electronlens is disposed in the vicinity of said sample, and a crossoverproduced by said electron gun, said electron lens and said NA apertureare in the conjugate relationships to each other.
 55. An electron beamsystem in accordance with claim 54, in which a crossover image of theelectron gun by said transmission electron beam is formed on or in thevicinity of a principal plane of said electron lens.
 56. An electronbeam system in accordance with claim 55, in which a shaping aperture isdisposed on a path of said primary electron beam, wherein said shapingaperture and said sample are arranged to be in the conjugaterelationship to each other.
 57. An electron beam system, in which anelectron image of secondary electrons emanated from a sample surface,back scattering electrons or an electron having passed through thesample is magnified by at least two-stage of electron lenses and thendetected, wherein a magnified image produced by a first stage ofelectron lens is focused on a certain point upstream to a second stageof electron lens to thereby reduce a distortion aberration or amagnification aberration.
 58. An electron beam system in accordance withany one of claims 54 through 56, in which at least two-stage of electronlenses are disposed on the path of said transmission electron beam,wherein a magnified image produced by a first stage of electron lens isfocused on a certain point upstream to a second stage of electron lens.59. An electron beam system, in which a primary electron beam isirradiated to a sample, and an image of secondary electrons emanatedfrom the sample, an image of back scattering electrons or an image oftransmission electrons having passed through the sample is magnified anddetected as an image, wherein a distortion aberration in the detectedimage is simulated by calculation to thereby determine a differencebetween a third order of absolute value and a fifth order of absolutevalue of the distortion aberration, and a compensation parameter isoptimized such that said difference is minimized or that the fifth orderof absolute value is greater than the third order of absolute value byabout 5 to 15%, wherein a position of a magnified image produced by afirst stage of electron lens is set in response to said optimizedcompensation parameter.
 60. An electron beam system in accordance withclaim 57 or 58, in which the distortion aberration in the detected imageis simulated by calculation to thereby determine a difference between athird order of absolute value and a fifth order of absolute value of thedistortion aberration, and a compensation parameter is optimized suchthat said difference is minimized or that the fifth order of absolutevalue is greater than the third order of absolute value by about 5 to15%, wherein said compensation parameter is a distance between saidsecond stage of electron lens and the magnified image, and the positionof the magnified image produced by the first stage of electron lens isset in response to said optimized compensation parameter.
 61. Anelectron beam system, in which electrons having passed through a sampleis magnified as a transmission electron image by an electron lensdisposed close to said sample so as to be detected by either one of aCCD, a TDI or an EBCCD, wherein when a magnification for magnifying saidtransmission electron image is to be changed, a distance between saidsample and said objective lens is changed.
 62. An electron beam systemin accordance with any one of claims 54 through 60, further comprisingan adjusting means for adjusting a distance between said sample and saidelectron lens disposed close to the sample when one sample is changed toanother.
 63. An electron beam system in accordance with any one ofclaims 44 through 62, in which said electron lens disposed close to thesample surface comprises an electromagnetic lens including a gap createdin the sample side.
 64. A manufacturing method of a semiconductordevice, in which a semiconductor wafer representing said sample to beinspected is inspected for any defect by using the electron beam systemdefined by any one of claims 44 through 53, claim 57, claim 59, claim 60and claim
 63. 65. A manufacturing method of a semiconductor device, inwhich a mask is used, which has been inspected for any defect by usingthe electron beam system defined by any one of claims 54 through 63.